ML22305A601
| ML22305A601 | |
| Person / Time | |
|---|---|
| Issue date: | 10/20/2022 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | |
| References | |
| NRC-2139, RG-1.082, Rev 5 | |
| Download: ML22305A601 (1) | |
Text
Official Transcript of Proceedings NUCLEAR REGULATORY COMMISSION
Title:
Advisory Committee on Reactor Safeguards Thermal Hydraulics Subcommittee Docket Number: (n/a)
Location: teleconference Date: Thursday, October 20, 2022 Work Order No.: NRC-2139 Pages 1-95 NEAL R. GROSS AND CO., INC.
Court Reporters and Transcribers 1716 14th Street, N.W.
Washington, D.C. 20009 (202) 234-4433
1 1
2 3
4 DISCLAIMER 5
6 7 UNITED STATES NUCLEAR REGULATORY COMMISSIONS 8 ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 9
10 11 The contents of this transcript of the 12 proceeding of the United States Nuclear Regulatory 13 Commission Advisory Committee on Reactor Safeguards, 14 as reported herein, is a record of the discussions 15 recorded at the meeting.
16 17 This transcript has not been reviewed, 18 corrected, and edited, and it may contain 19 inaccuracies.
20 21 22 23 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 www.nealrgross.com
1 1 UNITED STATES OF AMERICA 2 NUCLEAR REGULATORY COMMISSION 3 + + + + +
4 ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 5 (ACRS) 6 + + + + +
7 THERMAL HYDRAULICS SUBCOMMITTEE 8 + + + + +
9 THURSDAY 10 OCTOBER 20, 2022 11 + + + + +
12 The Subcommittee met via Video 13 Teleconference, at 9:30 a.m. EDT, Jose March-Leuba, 14 Chairman, presiding.
15 16 COMMITTEE MEMBERS:
17 JOSE MARCH-LEUBA, Chair 18 RONALD G. BALLINGER, Member 19 CHARLES H. BROWN, JR., Member 20 VESNA DIMITRIJEVIC, Member 21 GREGORY HALNON, Member 22 DAVID PETTI, Member 23 JOY L. REMPE, Member 24 MATTHEW SUNSERI, Member 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
2 1 ACRS CONSULTANT:
2 DENNIS BLEY 3 STEPHEN SCHULTZ 4
5 DESIGNATED FEDERAL OFFICIAL:
6 KENT HOWARD 7
8 ALSO PRESENT:
9 PAUL KLEIN, NRR 10 AHSAN SALLMAN, NRR 11 STEVE SMITH, NRR 12 JIM STECKEL, RES 13 14 15 16 17 18 19 20 21 22 23 24 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
3 1 P R O C E E D I N G S 2 9:30 a.m.
3 CHAIR MARCH-LEUBA: The meeting will now 4 come to order. This is a meeting of the ACRS Thermal 5 Hydraulics Subcommittee. I am Jose March-Leuba, the 6 Subcommittee Chairman. This meeting is being 7 conducted remotely via MS Teams.
8 I see the following ACRS members in 9 attendance, Ron Ballinger, Charles Brown, Greg Halnon, 10 Dave Petti, Joy Rempe, and Matt Sunseri. We also note 11 that our consultants, Dennis Bley and Steve Schultz, 12 are present.
13 Today's topic is Revision 5 of Regulatory 14 Guide 1.82, Water Sources for Long-Term Recirculation 15 Cooling Following a Loss-of-Cooling Accident. This 16 Reg Guide describes an approach to meet requirements 17 for water sources available for emergency core cooling 18 and other safety systems, like containment cooling.
19 This revision of the guide was issued in final form in 20 August 2022.
21 Let me give you a short introduction on 22 the history of this topic from my personal point of 23 view to remind the members of our past interactions 24 with the staff. Most relevant point is that this 25 provides guidelines for evaluating the adequacy and NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
4 1 the availability of water sources for long-term 2 recirculation cooling following a LOCA. It includes 3 the issues of the regeneration and the use of 4 containment accident pressure. ACRS has been involved 5 with both issues over a long time with multiple 6 meetings and letters. We have reviewed the 7 containment issue as part of the resolution of GS-191 8 and wrote letters agreeing with the staff approach, 9 including actual plant implementations.
10 On the issue of containment accident 11 pressure, or CAP, we wrote three letters in 2009, '10, 12 and '11 and concluded that credit for CAP should be 13 allowed only if plan modifications are not practical 14 and the use should be limited in amount and duration, 15 and it should include a risk assessment. We also 16 recommended that the guide, Revision 3 in 2009, should 17 be modified to recommend the type of analysis that the 18 staff will expect to credit CAP use. In my opinion, 19 Revision 5 implements our second recommendation, but 20 high-level disagreements may remain, especially on the 21 need for risk analysis. Members should keep this in 22 mind while we are reviewing it today because it is a 23 critical issue that will affect our letter.
24 Finally, even though it is not part of the 25 guide, I have asked the staff to give us their NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
5 1 perspective on the defense-in-depth that FLEX 2 equipment would provide in these type of accidents.
3 This is not part of our guide review, but this 4 provides useful information since (audio 5 interference). We are expected to have a full 6 committee meeting on this topic and likely write a 7 letter on November 1st. We expect that this meeting 8 will be conducted entirely over this public line.
9 Portions of our meeting may be closed to the public to 10 protect proprietary information, if necessary. If we 11 go to a closed line, we will have an opportunity for 12 public comments before we start the closed session of 13 the meeting.
14 The ACRS was established by a statute that 15 is governed by the Federal Advisory Committee Act, 16 FACA. As such, the Committee can only speak with 17 published letter reports. The ACRS section of the 18 U.S. NRC public website provides our charter, bylaws, 19 agendas, letter reports, full transcripts for the open 20 portions of all full or subcommittee meetings, 21 including the slides presented there.
22 The Designated Federal Official today is 23 Kent Howard.
24 A transcript of the meeting is being kept.
25 Therefore, speak into the microphones clearly and NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
6 1 state your name for the benefit of the court reporter.
2 Please keep the microphone on mute when not in use and 3 minimize the use of video feed to avoid bandwidth 4 problems for people assessing the meeting remotely.
5 At this point, I will give the floor to 6 the staff to commence their presentation. Jim, can 7 you go ahead.
8 MEMBER REMPE: Hey, Jose?
9 CHAIR MARCH-LEUBA: Hold on. Yes, Joy?
10 MEMBER REMPE: I'm sorry. Maybe it's just 11 my connection, but sometimes you cut in and out, and 12 I guess I don't know if other people have that problem 13 but I could not hear where you said in my opinion the 14 Reg Guide. Could you repeat what you said? Because 15 I --
16 CHAIR MARCH-LEUBA: Let find that part 17 because I have it written.
18 MR. BLEY: While he's looking, I don't 19 know --
20 (Simultaneous speaking.)
21 CHAIR MARCH-LEUBA: Do you have --
22 MEMBER REMPE: No, it's me, not someone 23 else. But would you repeat it for my own benefit 24 because I think that's an important statement I'd like 25 to hear.
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7 1 CHAIR MARCH-LEUBA: Yes. For the benefit 2 of everybody, let's see, let me change my --
3 (Simultaneous speaking.)
4 MEMBER REMPE: -- said he was fine, so it 5 may be just me, but just repeat it for me, please.
6 CHAIR MARCH-LEUBA: Do I sound better now?
7 MEMBER PETTI: Way better, Jose. Yes, 8 you sounded like you were on the end of a long 9 line.
10 CHAIR MARCH-LEUBA: Okay. So what I 11 said is, I'm repeating now, in my opinion, 12 Revision 5 implements our second recommendation, 13 that being that they have to document the type of 14 analysis that the staff expects to review to 15 credit CAP use, but high-level disagreements may 16 remain, especially on the need for a risk 17 analysis.
18 MEMBER REMPE: Thank you very much.
19 CHAIR MARCH-LEUBA: So, basically, there 20 were two recommendations. One is whatever the staff 21 expects from an applicant to take credit for CAP, they 22 need to document it, and that's what Appendix B of the 23 Revision 5 is. But we also had a recommendation that 24 maybe we do some risk analysis with this modification.
25 Okay. Any more comments before we move to NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
8 1 the staff? No? Jim, staff, go ahead.
2 MR. STECKEL: Thank you, Jose. I'm going 3 to briefly open the camera just so you have an idea 4 who you're speaking with. I'm going to introduce 5 myself and the two technical leads responsible for the 6 revision of this Reg Guide 1.82.
7 My name is Jim Steckel, and I'm a Program 8 Manager in the Office of Research, Division of 9 Engineering, and was designated to be the project 10 manager on this particular revision. Ahsan Sallman, 11 a Senior Nuclear Engineer with NRR DSS, is one of the 12 revision engineers that worked on this particular 13 upgrade to the Reg Guide; and Mr. Steve Smith, Senior 14 Plant Systems Engineer, also with NRR DSS.
15 I'm going to briefly describe what we're 16 going to present to you today. We are going to talk 17 about the main changes in Rev 5, and these include the 18 following. GSI-191. This issue constitutes the main 19 body of the Reg Guide and Appendix A. The next item 20 is containment accident pressure, CAP. There will be 21 a brief CAP description and how it is accounted for in 22 Appendix B. Also to be discussed is how this revision 23 provides some background on the relation of Reg Guide 24 1.81, Revision 5, to GSI-191, including a summary of 25 the GSI-191 issue, changes made in Reg Guide 1.82 for NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
9 1 GSI-191, and Reg Guide 1.82 status with respect to 2 GSI-191.
3 Additionally, we'll touch on Revision 5 4 public comment resolutions. And, finally, we'll 5 discuss the role of FLEX equipment regarding defense-6 in-depth.
7 I would now like to turn over the screen 8 to Steve Smith. Thank you.
9 MR. SMITH: Okay. We're just rearranging 10 here so that we can be in front of the camera and 11 control the screen. I guess we'll turn the camera off 12 to save bandwidth, as you recommended.
13 I'm going to try to go to the next slide.
14 CHAIR MARCH-LEUBA: We can see it.
15 MR. SMITH: There we go. All right. I'm 16 going to turn my, I'll turn the camera off here so you 17 pay more attention to the slides.
18 Okay. So this is slide two. We have the 19 presentation split up into two parts. I'm Steve 20 Smith, and I'm going to talk about the main body of 21 the Reg Guide and Appendix A. Those two we had 22 relatively minor changes to just to update references 23 and add some information about GSI-191 things.
24 Ahsan is going to talk about Appendix B, 25 which is a new appendix for containment accident NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
10 1 pressure, or CAP. It's just easier to say CAP, so 2 we're going to say CAP. I will also talk about the 3 public comments. We just did a very high-level 4 summary of that, and then we have a couple of slides 5 that also talk about how FLEX could provide defense-6 in-depth for these two issues.
7 This slide just provides a brief 8 description of the technical changes and the 9 applicability for Appendix B, and you'll see more 10 about that later on. So I'm going to move on to slide 11 three. If you have any questions at any time, just go 12 ahead and let me know and I'll stop and try to answer.
13 All right. So this is slide three, and 14 I'm going to be just providing a brief background on 15 GSI-191. This slide shows a few of the additions we 16 made to the Reg Guide and, in parentheses, we have the 17 approximate times that the NRC staff positions were 18 developed or items were published. So some of these 19 have some items published or letters sent, you know, 20 providing guidance to the industry.
21 All right. The next few slides, slides 22 four through seven, this might not make any sense, but 23 this is a brief long history. This slide shows the 24 pre-GSI-191 highlights. I'm not going to spend a lot 25 of time sitting on any of these slides, so I'm just NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
11 1 going to let you guys take a look through it and if 2 you have any questions. On this slide, this is 3 everything that occurred -- not everything. This is 4 a lot of the things that are related to the GSI-191 5 issue that occurred prior to the time that GSI-191 was 6 initiated.
7 The next slide shows the initial NRC 8 actions with respect to GSI-191. So it was actually 9 initiated in 1996, and then, starting in 2003, we sent 10 out a bulletin. In 2004, we sent out the General 11 Letter 0402, which is still ongoing. The GSI remained 12 open for a long time because some of the technical 13 issues were not fully understood, and we'll talk about 14 that a little bit on the next slide.
15 This slide, slide six, is the more recent 16 GSI history, and the things that really slowed the 17 closure down were chemical effects and in-vessel 18 effects were not well understood when we sent the 19 issue out to industry for resolution. Chemical 20 effects methodology was relatively quickly resolved, 21 and we had an acceptable method in 2007. But the in-22 vessel effects methodology was really not accepted by 23 the NRC staff until 2019. And chemical effects do 24 interrelate with in-vessel effects, so there was some 25 interplay there, too.
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12 1 But, anyway, for stringers, the chemical 2 effects were figured out by 2007, and then in 2019 we 3 figured out how to resolve in-vessel effects and we 4 put some guidance out for that.
5 Once we understood -- yes?
6 MR. BLEY: This is Dennis Bley. I've been 7 working my brain trying to remember some of this 8 history as it went on. Wasn't it during the chemical 9 effects investigations that we had some contradictory 10 experiments that took some time to get worked out? I 11 don't quite remember how that was settled.
12 MR. SMITH: I'll tell you what, I'm hoping 13 that Paul Klein is on the line, and he might be able 14 to help us out with that because he's our chemical 15 effects expert. Are you on, Paul?
16 MR. KLEIN: Yes, Steve, I'm on. This is 17 Paul Klein. So I guess a very short summary of how 18 the chemical effects evaluation happened, as Steve 19 mentioned, we understood early on after initial 20 testing that chemical effects could be a problem, but 21 there really wasn't a very good understanding of 22 timing with respect to chemical effects. So that took 23 quite a bit of time to really fully understand timing.
24 We knew that, if chemical effects occurred, it could 25 cause very large head losses.
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13 1 And so the contradictory testing that I 2 think you're referring to is some of the early in-3 vessel tests where they added the pre-mixed 4 precipitate. The actual head loss that was incurred 5 by chemical effects was really dependent upon the 6 particulate and fiber bed that had formed at the inlet 7 to the fuel. So I think that, over time, the 8 particulate-to-fiber ratio, when the composition of 9 the bed at the fuel inlet became better understood 10 and, more importantly, the timing became understood.
11 And then as alternate fuel paths were evaluated, it 12 became clear that, for most plants, in-vessel chemical 13 effects would not occur until after the point where 14 there was sufficient alternate water paths into the 15 vessel.
16 MR. BLEY: Thanks. That helps.
17 MR. SMITH: All right. Thank you, Paul.
18 So the last thing, as we sort of just discussed, the 19 last thing that was not resolved for GSI-191 was the 20 understanding of in-vessel effects. Once we provided 21 a guidance for how to resolve the in-vessel effects, 22 GSI-191 was closed because all the technical issues 23 were well enough understood to make that happen.
24 However, plants that have not responded 25 adequately to Generic Letter 0402 are still required NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
14 1 to respond. And on the next slide, I have a summary 2 of what the status is for all the plants. This is 3 slide seven coming up.
4 Okay. So this shows the status of the 5 plants. At the top are the deterministic plants, and 6 at the bottom is where we stand with risk-informed 7 resolution. So we had nine low-fiber plants that 8 closed out using the original in-vessel guidance, 9 which was probably at least ten years before the final 10 in-vessel guidance. And then we had ten plants close 11 out deterministically after we released the 2019 12 guidance. We have seven plants that have 13 deterministic submittals under review and two plants 14 we haven't received their final in-vessel submittals 15 yet.
16 And then we have six plants that are using 17 a risk-informed resolution. Two plants are closed.
18 South Texas was the first one, and Vogtle was the 19 second one. And those were -- STP did not use the new 20 in-vessel guidance, but Vogtle did. And you guys 21 looked at both of those large or safety evaluations 22 that we wrote. We have two plants under review, and 23 we have two plants that are planning on sending risk-24 informed license amendment requests in.
25 Okay. Slide eight, we're going to shift NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
15 1 gears a little bit. This just shows some of the 2 things that we changed or added to the Reg Guide. The 3 first thing is we added a reference to the draft Reg 4 Guide 1.229 for risk-informed evaluation. This is 5 what licensees have been using, that draft Reg Guide, 6 when they submit risk-informed LARs to us.
7 And then we also did a BWR evaluation of 8 lessons learned. Since the BWRs closed many years 9 ago, we've learned quite a few things, and they did a 10 lot of work and NRC staff did a lot of evaluation to 11 ensure that they had adequately addressed the major 12 areas.
13 On slide nine, this shows the changes that 14 were made. This is the biggest changes to in-vessel 15 downstream effects, so we did the safety-significant 16 technical evaluation report, which the ACRS looked at.
17 And we also developed the review guidance for the same 18 issue. And I just tried to put the important 19 references here.
20 One of the other important references is 21 on slide ten, and that is the WCAP-17788, which is --
22 was a large body of work that industry did to help us 23 understand the issue. And then back on slide three, 24 there was a few other things that we added. I didn't 25 put the numbers down for those, but we added NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
16 1 references to cover those, as well.
2 On slide 11, this is kind of a wrap-up as 3 far as GSI-191 and Reg Guide 1.82. We expect this 4 revision to be basically inclusive of all our guidance 5 for GSI-191. We understand that, you know, we may 6 learn a few things in the future and we might make 7 some minor changes, but this is basically the last 8 revision we're going to make to the Reg Guide for this 9 issue.
10 The other thing that's kind of important 11 is the rulemaking 10 CFR 50.46(c) is still with the 12 Commission. And so that may get, that may change the 13 way that we do risk-informed LARs. The only thing is 14 this rulemaking has taken such a long time that we 15 think we'll have all the risk-informed LARs probably 16 done before the rule is actually implemented. So kind 17 of depending on how that rulemaking goes, we'll decide 18 what to do with the draft Reg Guide 1.229 on the risk-19 informed evaluation of the issue. Now --
20 MR. SCHULTZ: Steve, this is Steve 21 Schultz. Before you go on, so the Reg Guide right now 22 is still a draft guide?
23 MR. SMITH: Yes, 1.229 is still draft.
24 MR. SCHULTZ: Still a draft guide. And 25 right now there is no further work that is ongoing, NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
17 1 and it will depend upon what the Commission determines 2 with regard to the rulemaking.
3 MR. SMITH: We didn't think it was 4 appropriate to finalize that Reg Guide because it is, 5 it's right now connected to the rulemaking. So we 6 didn't want to finalize or go any further with that 7 draft Reg Guide until the rulemaking is complete.
8 MR. SCHULTZ: The risk-informed submittals 9 you've already reviewed and they're coming in are 10 using the draft?
11 MR. SMITH: They are using the draft, yes.
12 MR. SCHULTZ: Good. Thank you.
13 MR. SMITH: Okay. So at this point, I am 14 pretty much done with the GSI-191 part of this. I 15 have slides on public comments and then how FLEX 16 provides, can provide defense-in-depth for the issue.
17 It's up to you whether we do those now, or we can do 18 them at the end if that seems more appropriate.
19 Whatever you guys, the ACRS Committee members think 20 would be the best thing to do. I can either go 21 through those now, or we can wait until after the CAP 22 presentation.
23 CHAIR MARCH-LEUBA: I think you're on a 24 roll. Let's keep going. You're doing well. Just 25 continue on this. It makes sense to finish this.
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18 1 You're doing well.
2 MR. SMITH: Okay, all right. So we're 3 going on to slide 12, and this is just these public 4 comments. We didn't go into a lot of detail here. We 5 didn't receive a ton of public comments. We received 6 four sets of public comments from three entities, and 7 I list the areas here. They were basically 8 applicability and scope definitions, clarifications, 9 and references, and add risk-informed guidance. And 10 for these, we made changes where we thought it was 11 appropriate.
12 We didn't think that Rev 5 was intended to 13 cover new reactors, except where the guidance would be 14 applicable to them. There was some comments that 15 thought that we should make it clear that this was not 16 applicable to new reactors, and that wasn't the intent 17 of this revision. Maybe the next revision will be 18 more specific with that, but we didn't do any work to 19 try to make this applicable to new reactors. So we 20 just expect them to use the guidance if it's 21 applicable.
22 And then we made some minor changes just 23 for clarifications and references, and we did not add 24 risk-informed guidance. We're awaiting the 50.46(c) 25 rulemaking. That was one of the comments. And I NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
19 1 think we have a couple more.
2 On the next slide, slide 13, there were 3 some comments that said we should be more specific 4 with the methodology, and the NRC thought that the 5 methodology was adequately specified. We did change 6 some references to make them public so that, you know, 7 people could look at those. And, basically, editorial 8 comments we incorporated.
9 Okay. We're going to move on to talk 10 about FLEX a little bit in slide 14. Okay. Now, the 11 thing about the FLEX is we are not FLEX experts. So 12 we talked to some people who worked on, we got input 13 from them to help create these slides. What we 14 figured out is BWRs have direct RCS injection points 15 that include high-volume flow, and those injection 16 points are predetermined and set up so they can just 17 take the FLEX equipment and pick it up and it will 18 inject to the RCS.
19 PWRs have some low-volume RCS flow and 20 high-volume steam generator flow. So if there was a 21 LOCA, and it was a large LOCA, they don't have pre-22 existing connection points to provide high-volume flow 23 to the RCS. They have, you know, they could provide 24 probably tens of gallons.
25 So the guys we talked to who reviewed this NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
20 1 for the BWRs and PWRs, they said that they could 2 reconfigure, plants could probably reconfigure the 3 steam generator pumps to inject to the RCS, but it's 4 not pre-set-up. It would take time, and it's kind of 5 a plant-dependent thing. So it depends how the plant 6 is designed and how their FLEX equipment is designed 7 as to how easy it would be to do that.
8 So with that in mind, we can go through 9 the next couple of slides. I kind of went through 10 slide 14 there, and then this slide 15 provides just, 11 slide 15 talks about strainer blockage, and it's 12 relatively similar. We looked at relatively similarly 13 to CAP blockage or CAP, you know, if you've lost 14 containment accident pressure, which is shown on the 15 next slide.
16 But, anyway, for most strainer blockage 17 events, the pressure in RCS would be low. BWRs would 18 have no problem hooking up FLEX capacity. So we look 19 at BWRs as having pretty good defense-in-depth. And 20 as we discussed on the previous slide, the PWR FLEX 21 strategies may be less effective for long-term 22 cooling. The PWR injection to the RCS is on the order 23 of tens of GPM, but that does include boron, you know.
24 They would have borated water to inject. Those are 25 designed for pump seal leakage usually or shutdown NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
21 1 conditions where you'd have a very low requirement for 2 volume of flow.
3 So, generally, it seems to us that BWRs 4 have better defense-in-depth, then probably pretty 5 good defense-in-depth, and the PWR would not have as 6 readily available defense-in-depth. It might take, 7 you know, depending on how long it takes the plant to 8 hook a higher-volume pump up, that would be important 9 as far as defense-in-depth is available. Eventually, 10 they could get there, but it might take, you know, we 11 don't know how long it would take.
12 CHAIR MARCH-LEUBA: So this is Jose. I 13 ask you to think about this area, even if it's not 14 part of the Reg Guide. When we go visit the plant, we 15 see this beautiful FLEX equipment, and we wonder if 16 it's useful. And what I'm hearing is, and I'm jumping 17 to Appendix B at the CAP credit, if we give CAP credit 18 to a boiling water reactor and some additional 19 accident loses the pressure in the containment by 20 cooling it or venting it or whatever mechanism, FLEX 21 would provide some defense-in-depth and probably it 22 would not be cause of the accident in boilers.
23 MR. SMITH: That's correct. Slide 16 was 24 more focused on the CAP credit issue, although, you 25 know, the way that the FLEX equipment works is similar NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
22 1 for both. So we concluded that the BWRs would be more 2 likely to use FLEX equipment to provide RCS injection, 3 in the case of a loss of NPSH, would include both the 4 loss of CAP or a clogged strainer. And PWRs would 5 have challenges to do that because they'd have to take 6 time to hook up the larger volume pumps to the RCS.
7 MEMBER BALLINGER: This is Ron Ballinger.
8 I think we need to be a little bit careful since we're 9 on the record of using the words defense-in-depth. I 10 think what you're saying is that the FLEX equipment 11 may or may not augment existing defense-in-depth.
12 You're not saying that we don't have defense-in-depth 13 and the FLEX equipment doesn't help. So I think we 14 need to be a little bit careful of when we use the 15 word defense-in-depth in this context.
16 CHAIR MARCH-LEUBA: I think you're wrong.
17 The way I read it, I understand it, is it provides 18 additional defense-in-depth.
19 MEMBER BALLINGER: Right, right. That's 20 what I'm saying. We need to be careful about the 21 words and be careful that somebody doesn't read this 22 at some point and say, oh, my gosh, what do you mean 23 they don't have defense-in-depth.
24 CHAIR MARCH-LEUBA: Well, the reason why 25 I was asking this is to do a risk analysis in our NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
23 1 minds of if you lose your CAP and suddenly your pumps 2 just start cavitating, what do you do? And what I'm 3 seeing from the analysis the staff performed is, in 4 boiling water reactors, you just run to the FLEX 5 building and bring those pumps in, and you're out of 6 the problems.
7 MEMBER BALLINGER: Right.
8 CHAIR MARCH-LEUBA: In PWRs, you have to 9 think a little more. It's good to have them, but 10 they're not designed to plug in in five minutes.
11 MEMBER BALLINGER: Right. But you're not 12 starting from a zero defense-in-depth point.
13 CHAIR MARCH-LEUBA: Correct. And we'll 14 talk about it a little more on CAP, but my 15 understanding is it's more challenging for boiling 16 water reactors than for pressurized water reactors.
17 Okay. Staff, continue.
18 MR. SMITH: If I just go back, if you go 19 back to slide 14, that provides a little bit more 20 background. We say on there the FLEX strategies are 21 not, they're not designed for the events that we're 22 talking about now. They're for beyond design basis 23 external events that come from natural phenomena.
24 They're not for LOCAs or events that would be likely 25 to end us up using containment accident pressure.
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24 1 So this is exactly what the FLEX guides 2 were saying. We do need to be careful how we 3 characterize this. This equipment is not designed for 4 this kind of accident. However, it can provide some 5 mitigative capacity, and it seems like BWRs would have 6 better mitigative capacity than PWRs.
7 MR. BLEY: Yes, this is Dennis Bley. I 8 want to go back to what Ron was saying, and I guess 9 the main defense-in-depth here is the containment, 10 which ought not lose its pressure. And that's where 11 the old arguments were hanging about just a small 12 amount and not for long. And then we had an applicant 13 come in that was proposing what seemed like a large 14 amount for a very long time, and then you start 15 worrying about could something happen to the 16 containment.
17 So the fact that FLEX, which Steve said is 18 designed for something else, can be very helpful here 19 is common with a lot of places people have found they 20 can use FLEX that gives us really a backup for things 21 that we thought very good anyway. So, yes, I'm 22 agreeing with Ron and I think Jose fell in the same 23 position. We're pretty well okay here, and FLEX can 24 really help if you need it, which is very unlikely.
25 That's enough.
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25 1 MR. SMITH: Yes, I agree. I think, yes, 2 it's not part of the design basis, which is, you know, 3 what we're trying to do with this other thing. It's 4 just something additional that could be available.
5 So that was my last slide. I'm going to 6 turn it over to Ahsan unless there's other questions.
7 CHAIR MARCH-LEUBA: I think that's a good 8 plan.
9 MR. SMITH: Okay.
10 CHAIR MARCH-LEUBA: So we're moving now to 11 containment accident pressure.
12 MR. SMITH: Yes. Just rearranging the 13 room here. Be with you in a second.
14 MR. SALLMAN: This is Ahsan Sallman. I'm 15 in the Nuclear Performance Branch in DSS, and I'll 16 talk about the guidance for the use of the containment 17 accident pressure for the net positive suction head 18 margin for ECCS and containment heat removal pumps in 19 BWRs and PWRs.
20 So this is the contents showing, this 21 slide shows the contents with the topical background, 22 ECCS, the role of ECCS pumps, and the regulatory 23 requirements, use of CAP in NPSH margin, cavitation, 24 erosion, effect of non-condensables, gas, loss of 25 containment isolation, containment cooling if CAP is NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
26 1 used, illustration of the CAP available quantifying 2 margin, the guidance summary. And then I have a list 3 of acronyms and symbols if anybody wants to look at 4 this at the end of this presentation.
5 This slide shows the CAP issue. CAP is 6 used in determining the NPSH available for ECCS and 7 containment heat removal pumps, and this was highly 8 criticized by the ACRS during maybe 15 - 20 years ago 9 when there were a couple of LARs from Browns Ferry and 10 Monticello, which, because of the CAP issue, they were 11 using CAP and the review was, you have to hold or 12 suspend it because of this. Then at that time we 13 requested BWR Owner's Group to submit a topical 14 report, which is NEDC-33347, and the BWR Owner's Group 15 developed a standard approach for requesting CAP.
16 Then staff wrote a white paper, and that 17 documented the staff position for the CAP, usage of 18 CAP. And then we had some ACRS letters that were 19 written to EDO and showed what is a position of ACRS, 20 and that is, I've written them down here, CAP credit 21 should be limited in amount and duration, and the 22 operator reactions, if the control CAP should be 23 reliable.
24 The next slide is ACRS wanted SRP-622, 25 which is on the containment heat removal, to be NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
27 1 revised and include the risk information in the CAP.
2 And the ones that are on star (phonetic) -- these 3 recommendations of ACRS were incorporated in this Reg 4 Guide, like modification of the plant before we give 5 CAP credit and we show that it is practical or 6 impractical.
7 And then this report, Owner's Group report 8 which provided a standard approach for use of CAP, the 9 statistical method of calculating the uncertainty in 10 that BSH. So then other suggestions or other 11 recommendations from ACRS was a hardware modification 12 or risk studies would not be needed if CAP credit is 13 small in deterministic analysis.
14 Okay. There was an ACRS letter that was 15 written to the Commission chairman about a 16 disagreement between the ACRS and staff, and the ACRS 17 position was a CAP should be, the CAP credit should 18 show the deterministic analysis, as well as plant-19 specific PRA, that should be included. And the staff 20 position was not for the deterministic, not for the 21 PRA but only the deterministic analysis.
22 At that same time, staff requested a pump 23 consultant to give us the different -- on different 24 tasks, there were four tasks assigned to the pump 25 consultant, and these tasks are written down here in NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
28 1 this slide.
2 The next slide is --
3 CHAIR MARCH-LEUBA: Go back and let's 4 understand --
5 MR. SALLMAN: Yes, sir.
6 CHAIR MARCH-LEUBA: That 2011 letter is 7 our last, well, last position I know of. What the 8 staff is saying that, if you created CAP in your 9 analysis and you show your NPSH is acceptable, you 10 don't need to do anything else, you can take credit 11 for the CAP. And the ACRS position was that, for a 12 short time and if you don't use too much of your CAP 13 margin, that is certainly okay; but, if you want to do 14 it for more than a hundred hours, then maintaining the 15 containment pressurized involves a number of events, 16 like operator errors of omission or commission; 17 additional failures of containment, if you had a big 18 seismic event that necessitated the whole thing.
19 So is that your position, and this is the 20 position in the Reg Guide now that --
21 MR. SALLMAN: Yes. The Reg Guide position 22 is now that you do the deterministic analysis using 23 CAP. And if CAP is used -- then I'll go over that in 24 the new few slides. If the CAP is used, which is 25 above the vapor pressure at the suppression of the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
29 1 pool temperature, then that has to be, there should be 2 additional analysis which was recommended in this BWR 3 Owner's Group report, and that is what we do the Monte 4 Carlo analysis to show how much margin it is. And 5 that was what was recommended by the ACRS at that 6 time.
7 CHAIR MARCH-LEUBA: Yes. But after you do 8 an LAR, for example if you want to do a power operate, 9 and now you need a CAP credit --
10 MR. SALLMAN: Yes.
11 CHAIR MARCH-LEUBA: -- need before, are 12 the operators required to update the PRA with the 13 consequences of creating CAP? I mean, there should be 14 a branch on the PRA, a number of sequences that 15 include failure of containment after having the 16 accident where CAP is needed, and they're not required 17 to evaluate that?
18 MR. SALLMAN: Well, that is not in the Reg 19 Guide at this time because -- I'll go to the next 20 slide, what happened when the Commission paper was 21 submitted, the SECY paper was submitted to the 22 Commission, and then they worded on the Commission 23 paper, SECY paper, and that determined that there was 24 no plant-specific PRA required and only the 25 deterministic analysis with some recommendation that NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
30 1 are in this slide from the ACRS that are included in 2 the guidance.
3 CHAIR MARCH-LEUBA: From a technical point 4 of view and a logical point of view, I'm making a 5 change to my plan, just, for example, a power operate, 6 that requires me now to credit CAP for my ECCS pumps 7 to work as advertised, and they have to operate for an 8 amount of time, X hours. I would like to know what is 9 the condition of probability that the containment 10 pressure would remain high for those X hours and 11 consider if allowing operation for those six hours 12 introduces an additional risk. And my gut feeling is, 13 if we do the analysis, it would come out to be 14 irrelevant, I mean, very small. But we don't do the 15 analysis, the probabilistic analysis.
16 MR. SALLMAN: No, it is not in the 17 guidance.
18 CHAIR MARCH-LEUBA: Yes, I know. Okay.
19 Thank you.
20 MEMBER DIMITRIJEVIC: This is Vesna. I 21 just want to tell you, based on my experience, if you 22 can credit CAP, that's not part of the PRA model. You 23 don't ask that, so you just assume the pump will 24 operate with no issue with the NPSH. So I have not 25 seen, based on my experience, that, but I did not NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
31 1 really have a, I didn't really look at the latest that 2 CAP shows as, that probabilistic CAP shows as input in 3 the PRA model.
4 CHAIR MARCH-LEUBA: Yes, that is what I 5 was saying. The Reg Guide 1.82, that's not required, 6 and apparently nothing else requires it. And 7 logically, I mean, if we are going to be a modern 8 risk-informed regulator, we should know what the risk 9 is.
10 MEMBER DIMITRIJEVIC: Remember the PRA 11 cover only injection for 44 hours5.092593e-4 days <br />0.0122 hours <br />7.275132e-5 weeks <br />1.6742e-5 months <br /> after accident, I 12 mean, except for containment performance, which is 13 sometimes asked for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. But the coolant plant 14 in that period is only 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
15 CHAIR MARCH-LEUBA: The CAP credit for 16 preventing NPSH is a short duration. I mean, it's 17 maybe 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, right, Ahsan? What is typically the 18 time that you need a credit?
19 MR. SALLMAN: Well, we submitted this 20 guidance in the form of an interim guidance to the 21 owner's groups and we received some LARs on EPUs that 22 were reviewed by the staff and the ACRS. And 23 following this guidance, some of them, they did not 24 use CAP. They improved their plant, one of them, they 25 improved their plant. But mostly, in Appendix R NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
32 1 analysis for the fire, Browns Ferry was using several 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> of CAP; I don't remember exactly how much, but 3 that was an issue when this whole thing started in 4 2007 - 2009 and that review was suspended.
5 But the duration was, in Appendix R 6 analysis, they used maybe more than 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br /> or 7 something.
8 CHAIR MARCH-LEUBA: Yes, 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br /> --
9 MR. SALLMAN: I'm not sure whether the 10 number, but it was a very high number.
11 CHAIR MARCH-LEUBA: Yes, 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br /> is not 12 a very high number to keep the, when you're talking 13 about containment integrity, in my opinion. If you 14 have to --
15 MEMBER REMPE: Well, just --
16 (Simultaneous speaking.)
17 CHAIR MARCH-LEUBA: -- that would be --
18 MEMBER REMPE: But to give some more 19 background.
20 CHAIR MARCH-LEUBA: Yes. Okay. Dennis --
21 MEMBER REMPE: But to give some more 22 background, Browns Ferry got rid of their CAP credit 23 before they got --
24 MR. SALLMAN: Yes, that is correct. They 25 got rid of the CAP credit by improving the heat NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
33 1 exchanger performance parameter, the K value of the 2 heat exchanger, and so did Peach Bottom. They got rid 3 of the CAP by putting a cross tie between the two 4 loops of the RHR heat exchanger. And some of the BWRs 5 are using CAP, but the CAP is less than the vapor 6 pressure at the sump temperature, and that is allowed 7 in the guidance. So I'll go over that in the next few 8 slides.
9 CHAIR MARCH-LEUBA: Just a moment. Dennis 10 has a comment.
11 MR. BLEY: Yes, I just wanted to weigh in 12 a little here. Back when all this was going on, and 13 I forget the exact number for Browns Ferry, but they 14 were out there a pretty long time needing the CAP 15 credit. The staff, Marty Stutzke, presented kind of 16 a generic back-of-the-envelope look at the risk, which 17 showed it was quite low. And I think most of the 18 members agreed with that but thought that it was 19 important to take that look on a plant-specific basis 20 to make sure there wasn't something in a particular 21 plant that would be challenging, and that's kind of 22 where the argument ended.
23 MR. SCHULTZ: Dennis, this is Steve, and 24 Ahsan, as well. The point that you've just made about 25 addressing the issue on a plant-specific basis is NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
34 1 important, and, as you were speaking about resolution, 2 Ahsan, one of the ACRS's, their comments was that, 3 rather than to use CAP credit, plants should 4 investigate and see if there were changes that could 5 be made to the plant design that would either 6 eliminate or lower the need, reduce the need for CAP 7 credit in the event of an accident.
8 MR. SALLMAN: Yes, that is correct. This 9 guidance is included that they should look at a plant 10 modification before they take credit, and they should 11 say that this is, they should tell us that this is 12 impractical to modify the plant, and then we can allow 13 them the CAP credit. That was one of the 14 recommendations from ACRS also and the staff.
15 MR. SCHULTZ: I appreciate your listing of 16 the number of elements that were provided by the ACRS 17 to the staff, and, obviously, there were several 18 discussions associated with it, and you've provided a 19 good indication of what the staff had agreed to with 20 regard to the ACRS recommendation and had implemented 21 in the going forward processes.
22 MR. SALLMAN: Right. Those are in the, 23 the asterisks in this, on slide 20 show those ones 24 that were included in the guidance. Okay.
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35 1 which is still the SECY paper that was written by the 2 staff gave two options. One was the staff approach to 3 use a deterministic to calculate uncertainty in 4 margins, and the option two was the ACRS 5 recommendation to use the staff approach plus a plant-6 specific PRA. So the Commission voted for option one.
7 Then the SECY paper was approved, SECY-11-0014, with 8 option one.
9 So now there's the Reg Guide, Rev 5, 10 Appendix B, that we are presenting here is based on 11 the SECY paper enclosure one. Enclosure one is this 12 subject of the CAP.
13 Okay. This slide is just showing what the 14 definitions of NPSH, available NPSH, and the CAP. So 15 I'll go to the next one. Okay. Here is the 16 definition of required NPSH which the vendor is 17 supposed to provide, and that definition, according to 18 the Hydraulic Institute Standard 14.6, and that is 19 NPSH results in cavitation sufficient to reduce the 20 pump total dynamic head by three percent. And the 21 figure shows at different flow rates the drop in the 22 dynamic head, and that's where the NPSH is. And the 23 NPSH margin is defined, we defined it as available 24 minus the required, and the required is what is given 25 to us by the vendor.
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36 1 I'll go to the next slide. And then 2 there's another term that we use here, NPSH margin 3 ratio, and that is a ratio of the available to the 4 required NPSH.
5 Okay. In the BWRs, the two systems, RHR 6 system and the low-pressure coolant injection -- I'm 7 sorry -- the low-pressure based system, these are the 8 ones that are the main systems, they're pumps. They 9 draw water from the suppression pool and spray the 10 vessel by the LPCS and the RHR is LPCI injection, the 11 low-pressure coolant injection, drawing water from the 12 suppression pool. So when the suppression pool gets 13 higher in temperature, that's when its vapor pressure 14 increases and that's when the CAP is requested. In 15 the PWRs, the safety injection pumps in the 16 recirculation mode of the PWR and also the containment 17 spray cooling for efficient products removal and 18 cooling of the containment. So those are the pumps 19 that mainly require CAP for the NPSH.
20 CHAIR MARCH-LEUBA: Ahsan, in the 21 analysis, containment spraying has two effects. It 22 removes contamination, of course, but it helps cool 23 the containment and gives you additional NPSH and the 24 sump conditions margin.
25 MR. SALLMAN: Exactly. That's because NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
37 1 NPSH is, the available NPSH is a transient thing, and 2 that keeps on changing as the transient goes on.
3 CHAIR MARCH-LEUBA: So if you turn on the 4 spray, there is a race. You know, on the one side, 5 you start lowering the pressure of the CAP, lowering 6 the pressure in containment. On the other side, you 7 also increase your margin.
8 MR. SALLMAN: Yes.
9 CHAIR MARCH-LEUBA: So the calculation 10 from the Reg Guide procedures requires you to do the 11 calculation properly for --
12 MR. SALLMAN: Yes, yes. The calculation 13 of the containment, calculation consists of the 14 suppression pool or the sump temperature conservative 15 calculation of the suppression pool with conservative 16 inputs and also for the PWRs the sump calculation, 17 sump temperature calculation, which are transients.
18 So based on those temperatures of the sump temperature 19 or the suppression pool temperatures, the NPSH is 20 calculated, the available NPSH is calculated.
21 CHAIR MARCH-LEUBA: Yes. But my point, 22 maybe I'm not really properly -- containment spray is 23 likely to be an operator action.
24 MR. SALLMAN: Yes.
25 CHAIR MARCH-LEUBA: Which will happen at NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
38 1 random times. The procedure will tell you one thing, 2 and the actual human factors engineer will tell you 3 something else. And I see it's a difficult 4 calculation because you're likely to reduce the 5 pressure of containment faster than you will reduce 6 the temperature of the sump.
7 MR. SALLMAN: Yes. When they do the 8 analysis for the containment cooling or the 9 suppression pool cooling, they follow whatever the 10 procedure is, and the safety analysis is based on --
11 like for BWRs, there's ten minutes allowed for the 12 operator action to switch from the LPCI mode to the 13 containment, to the suppression pool cooling mode. So 14 that is an operator action, and the PWRs, PWRs, 15 mainly, it is at the sump recirculation mode when the 16 containment sprays are initiated. So that is, more or 17 less, several minutes, I think, maybe a half an hour, 18 after a LOCA, a large-break LOCA initiation. So 19 there's plenty of operator refinement; and if they 20 follow the procedures for the containment spray, 21 that's how the calculation analysis is done.
22 CHAIR MARCH-LEUBA: Okay. Thank you.
23 MR. SALLMAN: The recirculation is, you 24 know, in the BWR, it is more critical, the operator 25 action is more critical because it's only -- but the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
39 1 PWRs, there's a lot of time before the sump flow is 2 initiated.
3 Okay. Go to the next slide. The 4 regulatory requirements are GDC 35, which is for the 5 safety, for the RHR LPCI injection, and the GDC 38 is 6 the containment heat removal for both, and that is RHR 7 pump on the containment spray pumps.
8 The guidance initially was also included, 9 some of the guidance was included in the Reg Guide 10 1.82 before this revision, and that is in this section 11 which I've noted here, 131, which requires 12 conservative calculation for the transients and for a 13 typical test for crediting containment operation and 14 cavitation, calculation of the pump water temperature 15 and head loss in the suction strainer.
16 Okay. The uncertainty analysis and the 17 NPSH margin, that was a recommendation also from the 18 ACRS following the BWR Owner's Group topical report, 19 which provided us with a Monte Carlo calculation to 20 calculate the margin, and that was also recommended.
21 And then special, for special events, which is, in the 22 BWRs, it's station blackout event and Appendix R fire 23 event and an adverse event. Those three events are 24 the special events in which it was cited and agreed 25 upon that the realistic, instead of conservative NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
40 1 calculation, realistic inputs or nominal inputs can be 2 used.
3 CHAIR MARCH-LEUBA: And this is consistent 4 with how we analyze special events.
5 MR. SALLMAN: Right.
6 CHAIR MARCH-LEUBA: For all the other 7 analyses we do.
8 MR. SALLMAN: Right.
9 CHAIR MARCH-LEUBA: Nothing unusual about 10 it.
11 MR. SALLMAN: Right. So the use of CAP in 12 the -- okay. The NPSHR three percent, that is the 13 basis for the vendor testing. I think that is 14 provided by the vendor, and the NPSH margin, it was 15 recommended that we should include, in the margin we 16 should include the uncertainties because the pump is 17 tested in the factory and the field NPSH required may 18 be different. So that was one of the recommendations 19 also from the ACRS that we should include the 20 uncertainties and then compare the available with the 21 required, and that is called NPSHR effective, which 22 includes uncertainties because of the situations, 23 different situation in the testing. Testing may be 24 done with a different model speed or a different 25 configuration of the test setup, or it could be the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
41 1 air content in the -- so that is given in the next 2 slide. I'll talk about that also.
3 Pump speed is one of the factors that 4 would affect the difference. Water temperature, the 5 water temperature which is different at the factory --
6 the water temperature was recommended not to be 7 considered because if there's an increase in the water 8 temperature at the site, that means that NPSHR would 9 go down. So that was not included in this guidance.
10 The third one is a suction, the suction 11 piping configuration, which is different. So that is 12 another uncertainty. And the last one is the air 13 content in the water, which may be different at the 14 site.
15 So all these uncertainty values were 16 evaluated by the staff with a pump consultant. He 17 gave us the guidance on how to use these 18 uncertainties.
19 So it was decided and it was also 20 recommended by the ACRS to use the NPSHR effective, 21 which includes uncertainties in the NPSH for the DBA 22 LOCA. And for the special events, for the BWR special 23 events, station blackout and Appendix R events, you 24 can use the three percent which is provided by the 25 site.
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42 1 The ones that we reviewed, some of the 2 EPUs that were reviewed, they decided to use 21 3 percent uncertainty, which is the pump consultant gave 4 us a bounding value of that. And the guidance says 5 either, you know, the plant licensee should come up 6 with a justification of the uncertainty, and they 7 decided to use what was suggested by the pump 8 consultant. That is in his report, 21 percent.
9 Okay. This slide shows if there's a 10 negative NPSH margin then it should be, then the test 11 should demonstrate that the pump will perform its 12 safety function. Operation for a limited duration, 13 less than a hundred hours. And if the test is done on 14 the actual pump or a similar model and the testing at 15 the same speed, so, in that case, if it is properly 16 tested using these recommendations, then the guidance 17 says that, yes, you can use negative margin.
18 CHAIR MARCH-LEUBA: Could you explain a 19 little? Go back to Slide 14.
20 MR. SALLMAN: Okay.
21 CHAIR MARCH-LEUBA: Negative NPSH margin, 22 even after applying the CAP? What do you mean by 23 negative margin?
24 MR. SALLMAN: Negative means NPSHa is less 25 than NPSHr.
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43 1 CHAIR MARCH-LEUBA: With or without the 2 CAP credit?
3 MR. SALLMAN: For DBA -- for DBA, it has 4 to be effective. Effective means uncertainty.
5 CHAIR MARCH-LEUBA: Yes.
6 MR. SALLMAN: If you use that -- if you 7 use that credit, so you use NPSH effective, and you 8 use CAP credit, and then that -- that means that you 9 have applied certainties and you compared NPSH --
10 availability of the NPSH required. So that's how you 11 come to the NPSH margin or the DBA.
12 And, similarly, for the special events, 13 you subtract available minus the fee percent NPSH.
14 CHAIR MARCH-LEUBA: So --
15 MR. SALLMAN: If there is a negative 16 margin -- if there is a negative margin in such cases, 17 I think which is very rare, you know, we haven't seen 18 such thing, but the guidance allows that, and then it 19 -- the pump is tested for these conditions.
20 CHAIR MARCH-LEUBA: So they're testing, 21 running the pumps with an NPSH negative.
22 MR. SALLMAN: Yes.
23 CHAIR MARCH-LEUBA: And it -- eventually, 24 the pump destroys itself. But for the first 25 100 hours, available to operate in a slightly NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
44 1 different mode, but not --
2 MR. SALLMAN: Well, I don't know if this 3 test has been done, but we are saying that this --
4 this is -- this is required to be tested if -- if the 5 licensee say we're going to operate a negative margin.
6 Okay. Then let's do this test.
7 CHAIR MARCH-LEUBA: Okay. But nobody is 8 really --
9 MR. SALLMAN: No. No, yeah. Yeah.
10 CHAIR MARCH-LEUBA: Yeah.
11 MR. SALLMAN: This is in the guidance.
12 CHAIR MARCH-LEUBA: Okay.
13 MR. BLEY: Can I -- can I jump in? This 14 is Dennis Bley again. I think for me -- and I kind of 15 think for most of the members at the time -- the 16 staff's pump consultant's reports were really 17 enlightening. At least for me, with an operating 18 background, I always thought you're losing -- loss of 19 suction head, you're done; the pump is gone.
20 But there is the idea that, you know, two 21 things that are happening. The pump, as you begin to 22 lose it and go negative, you -- and start cavitating 23 slightly, you lose pump efficiency, but you also start 24 doing damage. And there is a pretty extensive time 25 period before you really destroy the pump.
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45 1 So it was a very interesting set of 2 reports that they brought forward.
3 MR. SALLMAN: Yeah. You know, I have --
4 I have a backup slide on that. What erosion damage 5 would be done to the pump, it would be thousands of 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> I guess, I think it mentioned in this report.
7 That the erosion damage, because of the cavitation and 8 negative NPSH, pump operation could take -- take that 9 while operating several -- several hours, several --
10 I think it has been closing for thousands of hours.
11 MEMBER HALNON: Yeah. This is Greg.
12 Those low-pressure injection pumps and PWRs are very, 13 very robust. Matter of fact, I think they are 14 repurposed from old paper slurry, slur plants that 15 they use. So they are very resistant to any kind of 16 major or quick erosion or cavitation problems.
17 MR. SALLMAN: Okay. We'll go to the next 18 slide. So this slide is presenting on the cavitation 19 erosion, insufficient NPSH margin resulting in pitting 20 of the propeller blade and other pump parts due to 21 condensation caused by the vapor bubble implosion.
22 So the recent study, the acoustical 23 measurements experience shows maximum erosion rate 24 after the NPSHa value, which is between three percent 25 and the cavitation's inception margin ratio of four.
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46 1 So this -- this slide shows the erosion 2 zone and cavitation, non-cavitating zone, the three 3 percent head drop curve.
4 CHAIR MARCH-LEUBA: So what was the story 5 of this slide and the previous discussion is that 6 there is no sharp edge at which you hit it, the pump 7 blows up, because it -- vibrating so much it kills 8 itself. It's a slow erosion, a slow degeneration, so 9 you can have cavitation for 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> for pumps and it 10 still survive.
11 MR. SALLMAN: Yeah. Even more than that, 12 the pump consultant report, it was -- and I can open 13 that backup slide if you want me to.
14 CHAIR MARCH-LEUBA: No need. I think I 15 hear what you're trying to say, that we always to 16 think you cavitate, your pump is just vibrating, and 17 it falls to the ground. And it's not the case. It 18 just has some erosion, has some vibration, has some 19 degrading, and eventually it will fail. But they are 20 very strong pumps.
21 MR. SALLMAN: Yeah.
22 CHAIR MARCH-LEUBA: Thank you.
23 MEMBER DIMITRIJEVIC: This is Vesna. I 24 just want to make a comment that at this time, I mean, 25 you hopefully recover your suction, because once you NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
47 1 fail those pumps, doesn't matter how many hours. You 2 are doomed. You don't have any more means to cool the 3 reactor, because those are your RHR pumps in the PWR.
4 So it doesn't matter, the last 1,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> 5 we have to recover section before they fail. I mean, 6 this is just my comment in this case, because those --
7 all the pumps you have available to cool the plant 8 down, you know, after you are shutdown. So --
9 CHAIR MARCH-LEUBA: I agree, Vesna. But 10 typically this loss of NPSH is important. Eventually, 11 you are going to cool down your suppression pool and 12 recover your NPSH, of course using these pumps. So, 13 the better one.
14 MEMBER DIMITRIJEVIC: Right.
15 MR. SALLMAN: Yeah. The number of hours 16 that -- that these pump operate for the safety-related 17 operation, that is -- you know, during those hours, 18 even if there is minor degradation taking place in a 19 pump, nothing will happen to the pump. That was from 20 the report, consultant's report.
21 Okay. Go to the next slide.
22 Effect of non-condensable gas on 23 mechanical performance. That -- that is also one of 24 the points that the pump consultant mentioned that the 25 -- that's why for -- for the entrained air from the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
48 1 suction source vortices or release pump solution can 2 affect the pump performance.
3 So the configuration of the PWR pump or 4 BWR suppression pool should consider eliminating 5 entrainment of air by spraying the vortices. These 6 are all guidance in there -- in this.
7 The last one is the time of operation in 8 the region of maximum relationship be limited.
9 Okay. This is one of the items that was 10 included in the guidance that if -- to demonstrate the 11 loss of containment isolation and containment leakage.
12 So if CAP is used, the licensee should demonstrate 13 that there is no preexisting leak in the containment.
14 And one of the -- one of the licensees --
15 I think Monticello -- they used CAP for I think 16 Appendix R analysis or the DBA LOCA also. They were 17 required to monitor the containment during plant 18 operation for preexisting leak. And this is how they 19 were monitoring, and that is also in the guidance.
20 In the EPU report that they gave us, they 21 included that -- that we will monitor the containment 22 during plant operation for a preexisting leak.
23 Another thing is, the licensee should 24 demonstrate sprays and coolers will not reduce the 25 needed CAP. Operator reaction to control CAP by NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
49 1 spraying a pool is acceptable, justified, and 2 operating procedures should include proper guidance 3 for operator action.
4 Go to the next slide.
5 CHAIR MARCH-LEUBA: Hold on. This is 6 Jose. Go back to there. The guide mentions -- I 7 don't know about which section -- that the risk for --
8 that the time -- that limiting the time at which you 9 can operate with CAP credit is not risk significant, 10 because the risk is controlled by preexisting leaks in 11 the containment, like this containment isolation, loss 12 of containment isolation, that you are talking about 13 at the time of the accident.
14 And the additional risk of the containment 15 development a risk -- a leak during the CAP credit 16 operation is very small.
17 Do you care to expand on that? I mean, is 18 this what you're saying here? That you mean that 19 raised by monitoring the containment before the 20 accident --
21 MR. SALLMAN: Yes. That is correct.
22 During plant operation, the licensee was using CAP --
23 either PWR or BWR -- and be required to monitor an 24 existing leak in the containment.
25 CHAIR MARCH-LEUBA: Right. But they --
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50 1 MR. SALLMAN: For that --
2 CHAIR MARCH-LEUBA: They got -- the 3 recommendation from ACRS was that CAP should only be 4 used for short periods of time, and the rationale 5 behind it in my mind is that you don't want to develop 6 a leak 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> after the accident.
7 But the argument in the guide is that 8 there really -- there should be -- there is no need to 9 put a serious limit on the CAP credit time because if 10 you do a risk analysis, you find out all the risk is 11 controlled by preexisting leaks.
12 MR. SALLMAN: Right. Right.
13 CHAIR MARCH-LEUBA: Is that correct?
14 MR. SALLMAN: So that is correct, that 15 initially it was short period of time. But when we 16 included these uncertainties in the analysis, and 17 tried to see that the plant has -- the NPSHa is 18 compared with NPSHr effective, then we are also doing 19 this containment monitoring prior to the accident, or 20 during plant operation we are monitoring the 21 containment for -- for preexisting leaks.
22 These are all guidance that are in this --
23 in this guidance, in this Reg Guide to minimize or to, 24 you know, to -- for acceptable CAP, that the CAP is 25 acceptable, or not just for short period of time but NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
51 1 they can use -- for the amount -- they're not really 2 necessary for the entire cooldown of the containment.
3 It could be -- some plan may be for short 4 period of time. Some plan may be during long-term 5 cooling. But it's -- it was initially for short 6 period as ACRS recommended. But with this guidance 7 that we have approved, or we have -- we have given to 8 the licensees, this will allow them to use the CAP as 9 needed, but to -- to use the CAP, then, to follow this 10 -- the guidance for the preexisting leak.
11 CHAIR MARCH-LEUBA: Okay. Thank you. You 12 can continue.
13 MR. SALLMAN: Thank you. Okay. This is 14 -- this is how the CAP is used, would be used for this 15 curve. This graph represents the containment 16 pressure. ATM is the containment pressure, and this 17 line here represents the atmospheric pressure or the 18 initial pressure in the containment before an 19 accident.
20 And during an accident, if the -- if the 21 pressure of the suppression pool or the sump goes 22 above -- above the vapor pressure at this -- at the 23 sump -- at the initial temperature, that's the -- this 24 line, HVP, is representing the vapor pressure at the 25 sump temperature or the suppression pool temperature.
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52 1 So if it is -- if the CAP is requested 2 within -- below this value, below this curve value, 3 the lower curve value, then that is mostly -- that is 4 mostly acceptable because you cannot -- if the 5 temperature in the pool is high, you cannot lose that 6 pressure.
7 So that is mostly PWRs. There is some 8 temperature goes higher than the 212 degrees, which is 9 atmospheric. So if that temperature -- if the 10 pressure goes -- the temperature goes higher than 212, 11 then the CAP is allowed to be used up to the vapor 12 pressure of the sump temperature.
13 If they -- if they are requesting CAP 14 above that, above that HVP curve, that means that now 15 they have to follow the guidance, which is a 16 preexisting leak monitoring and whatever is in this 17 guidance. And BWRs, mostly they -- their sump 18 suppression pool temperature scales below 212 degrees 19 during a LOCA, some of them which have notice that 20 goes slightly -- maybe slightly above 212. It's 220 21 degrees.
22 And if they -- if they are using CAP, they 23 are asking to use CAP, then for that situation, that's 24 similar to the -- that's going above the HVP -- HVP 25 curve. So that means that they have to follow the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
53 1 guidance of the preexisting leak, monitoring the 2 preexisting leak.
3 MR. BLEY: So, Dennis again. The HVP 4 curve --
5 MR. SALLMAN: Yes.
6 MR. BLEY: -- essentially we're saying 7 there, since that's arising from the kind of place you 8 end up after everything flashes and you -- you've 9 equilibrated, it would take a pretty big hole in 10 containment to really affect that very much.
11 MR. SALLMAN: Right. That's true.
12 MR. BLEY: So there's not much one could 13 -- could challenge on that one. Okay. Go ahead.
14 MR. SALLMAN: Yeah. So that's how the PWR 15 -- most PWRs that I have reviewed, they stayed below 16 that HVP -- HVP curve, and they are allowed without 17 any preexisting leak monitoring.
18 Okay. So now this slide is showing how we 19 want to quantify the monitoring for LOCA, perform 20 realistic analysis. Sorry, first they do the bounding 21 conservative analysis for the containment and NPSH, 22 both with bounding inputs, and perform realistic 23 analysis to determine the margin.
24 If the CAP is used, then in order to show 25 the margin, they are required to do the 95/95 lower NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
54 1 tolerance limit of Monte Carlo calculation to show the 2 margin. This Monte Carlo is only introduced in this 3 guidance in order for them to demonstrate that there 4 is -- there is margin, good margin.
5 And then for the DBA LOCA, the requirement 6 is that NPSH required -- should include uncertainty.
7 That is, the available must be compared with the 8 required, which is NPSHr effective.
9 But for the special events, it's only 10 realistic inputs for the NPSH analysis, like the 11 suppression pool or the sump temperature. Doing a 12 realistic analysis is acceptable, nominal inputs, and 13 -- and then NPSHr may be used without uncertainty.
14 That is a three percent provided by the vendor.
15 So this is how the margin is quantified.
16 MR. SCHULTZ: Ahsan?
17 MR. SALLMAN: Yes.
18 MR. SCHULTZ: This is Steve Schultz. Just 19 on the -- on this slide here where we're talking about 20 addressing these events with realistic analyses plus 21 uncertainty, I'm particularly interested in the BWR 22 special events. Have any of the licensees had 23 difficulties in applying the guidance in terms of 24 demonstrating that the results are favorable?
25 MR. SALLMAN: Not that I've known so far.
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55 1 I viewed Monticello, Browns Ferry, Grand Gulf, three 2 of them, and I didn't see any issues with them. I 3 think mostly Browns Ferry got rid of the CAP because 4 they demonstrated their heat exchanger performance was 5 much better, and they were doing the monitoring of the 6 heat exchanger also.
7 MR. SCHULTZ: Right.
8 MR. SALLMAN: And they got rid of the CAP, 9 but Monticello used CAP. Monticello is the only plant 10 that I know used CAP for Appendix R and for -- also 11 for DBA LOCA, I believe. I'm not sure, but this is 12 what I remember.
13 And they -- they did -- they followed this 14 entire guidance.
15 MR. SCHULTZ: Yes.
16 MR. SALLMAN: You know, the demonstrated 17 using effective -- NPSHr effective and NPSHa 18 available. And also they introduced the preexisting 19 monitoring of the previous D&D (phonetic). But the 20 special events also in Monticello I remember, only 21 that -- I think Appendix R.
22 MR. SCHULTZ: Okay. Thank you.
23 MR. SALLMAN: Yeah. Okay. This slide is 24 the guidance summary, which we have almost discussed 25 all of these things. But I just -- just to repeat NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
56 1 them here in the slide, that NPSH for DBA, it should 2 be compared with NPSHr effective, including the 3 uncertainty, especially when you can use three percent 4 NPSHr effective.
5 The flow rate that should be used for the 6 NPSHa analysis should be greater than the flow rate 7 used in the safety analysis. That is one important 8 point that is in there.
9 Loss of containment for venting, sometimes 10 I think procedure maybe -- maybe include venting of 11 the containment, but that should not be done if the 12 CAP is used.
13 CHAIR MARCH-LEUBA: This is Jose. And 14 that's accomplished via procedures, modifying the 15 EOPs?
16 MR. SALLMAN: This is one of the 17 requirements in this Reg Guide that if they -- any of 18 the procedures, if they're using CAP and any of the 19 procedures require venting, that should not be the 20 case.
21 CHAIR MARCH-LEUBA: But venting is in the 22 procedures to protect containment. I mean, you don't 23 vent unless it is absolutely necessary. It's a good 24 thing to say, hey, I want to protect my pumps, so 25 protect my pumps. But if you do it by destroying the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
57 1 containment --
2 MR. SALLMAN: That's a severe accident 3 situation, destroying the --
4 CHAIR MARCH-LEUBA: Yes, it is.
5 MR. SALLMAN: -- containment. That is not 6 the design basis. In the design basis scenarios, I 7 don't know if there is any plant that would do that, 8 but --
9 CHAIR MARCH-LEUBA: Not from design basis.
10 MR. SALLMAN: Not for design -- you're 11 talking about design basis. If any plant has some 12 procedure in which they talk about containment 13 venting, that should not authorize the CAP is used 14 (phonetic). That's one of the points in this 15 guidance.
16 CHAIR MARCH-LEUBA: Okay. And by CAP --
17 excuse me. If I --
18 MEMBER DIMITRIJEVIC: How about 19 containment cooling or containment spray?
20 MR. SALLMAN: Containment spray is one of 21 the safety -- one of the safety systems which is used, 22 and containments sprays are used. You know, that is 23 a normal thing for -- during a LOCA. I mean --
24 MEMBER DIMITRIJEVIC: No, no. Of course, 25 but that will cool the containment, and, therefore, NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
58 1 reduce the pressure also.
2 MR. SALLMAN: Yes. Yeah, of course. Of 3 course.
4 MEMBER DIMITRIJEVIC: So is that part also 5 -- you said that he monitors the containment pressure.
6 That means, you know, the impacts venting and cooling, 7 right?
8 MR. SALLMAN: I cannot say cooling.
9 Cooling is -- cooling is a regular item in the 10 containment safety -- you know, the safety analysis.
11 Containment cooling is a part of the safety analysis.
12 While venting --
13 CHAIR MARCH-LEUBA: What you're trying to 14 say, Ahsan, is that the analysis that determined the 15 CAP credit assumed that sprays were working.
16 MEMBER DIMITRIJEVIC: Okay. Well, that's 17 exactly --
18 MR. SALLMAN: See, the CAP credit can be 19 at any time during short term, long term, in the PWRs, 20 in the short term if it is -- well, the short term 21 does not require CAP in PWR, because it is only -- the 22 CAP is only -- would be required when the sump 23 recirculation starts.
24 That time -- that's -- that time if the 25 CAP is required, it means, you know, the sprays aren't NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
59 1 operating. But one -- if the CAP is required, one 2 should not have a procedure which includes containment 3 venting.
4 CHAIR MARCH-LEUBA: Okay. And then --
5 MEMBER DIMITRIJEVIC: So they have 6 included the cooling in the CAP calculation.
7 MR. SALLMAN: Yeah. The cooling is --
8 cooling is included in the analysis. The regular --
9 the safety analysis includes everything, all of the --
10 all of the systems that come in operation during 11 containment cooling during an accident.
12 CHAIR MARCH-LEUBA: Yeah. The issue will 13 be, Vesna, the inadvertent actuation of the spray when 14 it's not supposed to.
15 MEMBER DIMITRIJEVIC: Yeah. But the spray 16 is not -- you know, spray is actuated by the operator.
17 I mean, you know, like, for example, in PWR, if you 18 have a large LOCA and you switch to recirc, let's say, 19 in half hour, that's -- you know, those are all after 20 all -- this is all operator action. So that's what I 21 want to say. This is not something which happened 22 automatically, so it can be controlled by operators.
23 MR. SALLMAN: Yes, yes. Yeah. The 24 analysis does consider that action, operator action.
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60 1 much CAP is needed.
2 MEMBER REMPE: So this Joy.
3 MR. SALLMAN: Yes.
4 MEMBER REMPE: I guess I'm still thinking 5 about this loss of containment integrity. Venting 6 shouldn't occur during CAP use. When the Monticello 7 EPU came through, it was around 2013, and we were 8 still reacting to post-Fukushima insights.
9 And I know our letter -- at least I 10 thought our letter mentioned that as folks were 11 revising the severe accident (audio interference) that 12 that might be an issue. And I don't -- I think we 13 haven't seen anyone else that uses CAP for -- from the 14 BWRs or even -- and help me understand. How will the 15 staff ensure that there isn't any sort of operator 16 guidance that would conflict with what's here?
17 MR. SALLMAN: Can you repeat what -- the 18 question? Venting -- the regular analysis that we do 19 for safety analysis, based on which we determine the 20 CAP, would not include venting. If the CAP is used, 21 not including venting.
22 But I -- I am not sure how if you -- if --
23 when would the venting be opening and --
24 MEMBER REMPE: Well, there has been an 25 emphasis on early venting. In the revised guidance, NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
61 1 there has been an emphasis on early venting for severe 2 accidents, you know, for prevention and mitigation.
3 And I just am wondering how the staff will ensure that 4 that revised guidance doesn't conflict with this 5 guidance that says we shouldn't have venting.
6 (Audio interference), others, Jose, do you 7 understand what I'm trying to say?
8 MR. BLEY: Joy, this is Dennis. Let me 9 cut in. At least for me, you're cutting out. We're 10 missing part of what you're saying. But I think I get 11 your question, and I'll try to repeat it because I 12 think others missed out.
13 And that is during a severe accident, we 14 have severe accident guidance now that says to vent 15 the containment. But if we got that -- if we have --
16 we're melting the core, we're beyond our concerns here 17 about CAP. So I don't think -- I don't see how they 18 conflict.
19 And Joy was worried that that guidance 20 could lead people to vent when they're still trying to 21 maintain CAP. But if you've lost the core, you've 22 lost that game of maintaining CAP, unless I missed 23 what you were getting at, Joy.
24 MEMBER REMPE: Okay. So I apologize for 25 my connection. And I understand that it is in the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
62 1 severe guidance that this early venting is (audio 2 interference). So I guess I am looking into timing.
3 I mean, so basically, you're saying all the revised 4 guidance would wait until you really clearly see 5 you've had cladding heat up, and that there is some 6 sort of release before they would say we're going to 7 vent.
8 And so the timing is carefully monitored, 9 and there is no chance that the operators would vent 10 early and adversely affect this CAP use. And the 11 staff is aware of this (audio interference) 12 emphasizing early venting, and it will not occur at a 13 time -- for example, if you're trying to get rid of 14 hydrogen, and you're having oxidation of the cladding, 15 I just am wondering about, is the timing that precise 16 in that they would be careful that they are not 17 worrying about this long-term cooling capability?
18 I think you understand where I'm going, 19 Dennis, and --
20 MR. SALLMAN: Yeah, yeah, I understand.
21 But we are -- we are within the design basis. This 22 guidance does not go into the severe accident 23 scenario. So we are just talking about venting. Is 24 there a design basis accident? And the procedure --
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63 1 accident says, hey, you need to vent the containment.
2 That is not allowed if the CAP -- if they 3 use CAP, because, you know, then the lose the 4 pressure, and then of course it -- the pump will not 5 operate. But this is within the design basis. So 6 severe accident is a different, you know, area that 7 is --
8 MR. BLEY: What Joy is -- what Joy is 9 getting at -- and I suspect she has cut out for you 10 folks, too -- is that some of that guidance is trying 11 to jump the gun and save the containment by venting 12 it. And you don't have -- I'm still in the design 13 basis meter on the board. The operators are trying to 14 save the core. But at the same time, they have this 15 guidance saying to get an early jump on venting the 16 containment, and that one needs to be careful that 17 those two sets of guidance don't conflict.
18 And I -- I think that's a good point, and 19 somebody needs to -- to track that. I don't think it 20 -- I don't know that it goes in your guidance here, 21 but it ought to be somewhere.
22 MEMBER REMPE: Thank you.
23 MEMBER HALNON: Yeah, this is Greg.
24 MEMBER REMPE: Thank you, Dennis. That 25 helps. Thank you for interpreting.
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64 1 MEMBER HALNON: I think I'm a little 2 confused. We're talking now about an actual event and 3 what the procedures say as opposed to I thought this 4 was to be applied to the analysis that shows you can 5 credit containment pressure.
6 And I guess I'm confused now. Are we 7 still talking about the rules of a game to do the 8 analysis versus how operators actually respond? I 9 mean, I guess my question is, is this -- if the 10 analysis shows that -- and if you want to credit 11 accident pressure but the analysis shows that at some 12 point you have to vent, then you can't credit the 13 pressure at that point, or you have to change your 14 procedures to prevent venting.
15 MR. SALLMAN: That is correct, sir. If 16 the analysis is showing that you should not vent the 17 containment, if you want to use a CAP, and if -- if --
18 then there would be a different analysis. The 19 licensee -- if they say we want to vent the 20 containment during a design basis accident, then that 21 analysis would be a different analysis.
22 MEMBER HALNON: Right. And if you're 23 going to vent --
24 MR. SALLMAN: That is not --
25 MEMBER HALNON: Well, if you're going to NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
65 1 vent outside of your procedures that were part of the 2 analysis, then you're in a -- you're in a position of 3 declaring 50.54X and going outside your procedures 4 because something else is happening.
5 And as Dennis said, you are probably well 6 beyond the need for a containment pressure credit 7 anyway. So the analysis uses the procedures. The 8 procedures are followed by the operators. And if you 9 have to go outside of those procedures, that's one 10 thing. But if you follow the procedures that you've 11 used in the analysis, then you can credit the 12 containment pressure.
13 If the procedures are such that you can't 14 -- that you have to vent, then you can't credit 15 containment pressure.
16 MEMBER REMPE: Right. And I'm trying to 17 say that when somebody applies this analysis, they'd 18 better be careful that their procedures do indeed not 19 allow any sort of venting. Dennis put it well. There 20 is not a -- we're staying in the design basis region 21 here. I just want to make sure that that interface is 22 carefully monitored is what I'm trying to get at.
23 MEMBER HALNON: I agree, Joy, and that 24 should be part of the analysis and --
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66 1 point is guiding the licensee that there should not be 2 any venting in the procedure if they are using CAP.
3 It's like -- it's like a precaution I guess, or one of 4 the things that the licensee should consider or look 5 at. If they want to use CAP, they should not vent the 6 containment in their procedure. So that should be 7 consistent with the analysis and the procedure.
8 MEMBER HALNON: But the point I made is 9 that the operator is not during the response to an 10 accident is not -- it's not in his mind whether or not 11 he is crediting containment pressure or not.
12 MR. SALLMAN: No. But the procedure -- I 13 believe the procedure should be developed based on the 14 analysis.
15 MEMBER HALNON: That's what I'm saying.
16 MR. SALLMAN: Yes.
17 MEMBER HALNON: They have to follow 18 procedures. And if they follow procedures, they 19 should be fine, because --
20 (Simultaneous speaking.)
21 MR. SALLMAN: Yes.
22 MR. SCHULTZ: This is not -- this is not 23 an operator activity statement. This is a go or no-go 24 statement as to whether CAP credit can be used.
25 MEMBER HALNON: It's built into the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
67 1 procedural steps.
2 MR. SALLMAN: Yes.
3 Okay. The other items in this -- well, in 4 this slide, the likelihood of a preexisting leak, that 5 -- you know, during plant operation they should 6 monitor the containment for a preexisting leak. And 7 negative margin is acceptable, as we discussed about, 8 you know, that testing should be done.
9 Then the goal of maximum erosion should be 10 between 1.2 and 1.6. That was information that was 11 given to us by the pump consultant.
12 The topical BWR should follow the topical 13 report, which is -- which was submitted to NRC and 14 also there was an SER in that topical report, which 15 provided Monte Carlo, you know, uncertainty analysis.
16 For the PWRs, the CAP options are to use 17 the vapor pressure corresponding to the sump, sump 18 water temperature, or use a procedure similar to the 19 Owners' Group, Monte Carlo.
20 Emission time for the pump using CAP, to 21 include the recovery time from the accident. So these 22 are the guidance -- summary of the guidance, these few 23 bullets.
24 Okay. This slide is showing what EPU LARs 25 that were reviewed, and I was involved in reviewing NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
68 1 these LARs for the containment only. And the CAP, 2 Monticello, Browns Ferry -- and Monticello was, you 3 know, reactivated. Actually, it was suspended when we 4 started the SECY paper.
5 And Browns Ferry was also suspended, but 6 they resubmitted their LAR. Then other ones were 7 Peach Bottom. They modified the hardware. Grand Gulf 8 was fine. Turkey Point -- not using Turkey Point 3 9 and 4. St. Lucie, Point Beach.
10 All these PWRs, they -- they use the CAP 11 up to the vapor pressure. None of them used both the 12 vapor pressure and the sump pressure.
13 CHAIR MARCH-LEUBA: So just to understand, 14 all these plans are taken clearly for CAP.
15 MR. SALLMAN: They're -- no, I'm not 16 saying they're taking CAP. But they followed the 17 guidance. And Monticello is the only one which took 18 credit of the CAP. Browns Ferry, they did some 19 modification of the heat exchanger I think, a 20 monitoring of the heat exchanger.
21 Peach Bottom is the one that modified the 22 hardware. And when I say modified the hardware, it 23 means they follow -- they follow this guidance, did 24 not use any CAP after they modified the plant.
25 Grand Gulf did not -- as I remember, did NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
69 1 not use CAP. Turkey Point, St. Lucie, Grand Gulf is 2 a BWR, so they did not use CAP. Turkey Point, 3 St. Lucie, and Point Beach, these plants they use CAP 4 but up to the vapor pressure, which is allowed in the 5 guidance.
6 So the only plant that I can think about 7 is the Monticello that they used CAP, and they did all 8 the analysis according to this guidance, and they also 9 have a preexisting leak monitoring in the facility.
10 CHAIR MARCH-LEUBA: Let me see if I can 11 summarize. The use of containment accident pressure 12 credit is not widespread among the fleet. It's only 13 a few plants here and there.
14 MR. SALLMAN: Well, it is --
15 CHAIR MARCH-LEUBA: It's allowed.
16 MR. SALLMAN: Yeah. When it started, Reg.
17 Guide 1.1, which is the Safety Guide 1.1, only allowed 18 -- did not allow to use CAP. But then, at that time, 19 some plants were using some CAP, like, you know, 20 mainly the Browns Ferry and Monticello, they were the 21 one that was using a lot of CAP in the analysis for 22 DBA and Appendix R fire analysis.
23 And at that time, when they were using a 24 lot of CAP, at that time the whole thing started 25 between ACRS and the staff, and the reviews and then NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
70 1 these, you know, letters were written and the SECY 2 paper was developed.
3 But later on when we got the revised 4 Browns Ferry LAR, they did not use -- they 5 demonstrated by analysis that they have an improved 6 heat exchanger which did not -- which required --
7 which has enough performance of the heat exchanger 8 that it is able to cool the suppression pool without 9 using CAP. And the vapor pressure was -- and 10 especially the Browns Ferry Appendix R analysis was 11 using too much -- too much CAP.
12 CHAIR MARCH-LEUBA: Okay. Thank you.
13 Does any --
14 MEMBER REMPE: And I think, as I recall, 15 Monticello is a very low power BWR. So it was -- it's 16 a much lower power I guess is something to mention, 17 too, here.
18 MR. SALLMAN: Yeah.
19 MR. SCHULTZ: So, Ahsan, what you're 20 saying about Monticello is that they used the 21 guidance, but they didn't have --
22 MR. SALLMAN: Yes. If you --
23 MR. SCHULTZ: -- to take credit for CAP.
24 MR. SALLMAN: Yes. Yeah. This guidance 25 was in the form of an interim guidance that we sent to NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
71 1 the Owners' Group, and that's what they used.
2 MR. SCHULTZ: Then you mentioned other 3 analyses that -- where CAP credit has been taken. Are 4 all of the ones in the third bullet there EPU LARs?
5 MR. SALLMAN: Yeah. All of them are EPU.
6 MR. SCHULTZ: Okay. Thank you.
7 CHAIR MARCH-LEUBA: So, Ahsan, this ends 8 your presentation?
9 MR. SALLMAN: Yeah. These are the ones 10 that I reviewed. There was maybe some others which I 11 don't know, somebody else -- the staff may have 12 reviewed. But I don't know the status. But the ones 13 that I put here are the ones that I reviewed.
14 Yeah. This is the end of the 15 presentation, and if any more questions or any 16 questions, I can try to respond.
17 CHAIR MARCH-LEUBA: So, members, any 18 questions from the staff or discussion? I hear none.
19 I am going to --
20 MR. SCHULTZ: Excuse me. Jose, this is 21 Steve. I had a question for clarification. It was in 22 Steve's presentation where a comment was made that the 23 revised -- Rev 5 is for operating units, and then 24 there was a comment, something about additional 25 guidance could be provided for new reactor NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
72 1 applications. Did I get that right? That this is not 2 -- this is not available for guidance or the guidance 3 would have to be modified for any new reactor 4 applications?
5 And one reason I'm asking that is, as I 6 saw -- was looking at references for the review, the 7 last -- the last ACRS letter I saw where CAP credit 8 was discussed was for the USA PWR application. And 9 some issues came up in the -- in that review where CAP 10 credit was being supported by the -- by the PRA or 11 there was some suggestion that it could be supported 12 by the PRA.
13 And the ACRS wrote a letter that suggested 14 that the PRA for the USA PWR was not sufficiently 15 developed to make that determination, and that in the 16 final discussion that an approach that would use best 17 estimate plus uncertainty would be the appropriate way 18 to go.
19 I'm not sure how that finally got resolved 20 in the approval, but, again, there is a new reactor 21 application, and it came up also in EPR. I was 22 wondering, what is the plan for new reactor 23 applications with regard to CAP credit?
24 MR. SMITH: Okay. So this is -- this is 25 Steve Smith. I discussed the comments. And basically NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
73 1 for new reactors, we -- or the public comments I 2 should say to make it -- make it clear. I discussed 3 the public comments.
4 Ahsan may want to jump in and discuss how 5 we would apply this to new reactors.
6 The reactor designs that you're talking 7 about are similar. Do you -- as far as GSI-191 stuff, 8 these reactors used basically the same guidance that 9 the reactors -- you know, the operating reactors used 10 for strainer and -- strainer testing, strainer issues, 11 and all that.
12 As far as CAP is concerned, I think we're 13 still -- we're still saying that if this guidance 14 would be applicable to those reactors, which I believe 15 it would be, it should be used.
16 We were not looking forward to the newer 17 -- you know, we weren't trying to do these reactors 18 that are going to be different. You know, they're 19 going to be, you know, molten salt reactors or that 20 kind of thing. We weren't trying to write the 21 guidance to be applicable to those kind of reactors.
22 But if it's applicable, if these are light-water 23 reactors, there is a good chance that this -- at least 24 some of the guidance that's included in this revision 25 of the Reg Guide is going to be applicable to them.
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74 1 MR. SCHULTZ: And going back to the public 2 comments, then, there were a number of comments that 3 were made by NuScale. And I -- I think you may want 4 to expand on what you just said because I -- my 5 impression was that NuScale was saying that -- that 6 the guidance should be adjusted because in their 7 designs there is equipment that is described that 8 isn't in the NuScale design.
9 Could you elaborate on the NuScale 10 comments and how you've responded to those?
11 MR. SMITH: Right. So for those comments, 12 basically what we said, we -- we have responded 13 relatively generically, and we said that they should 14 look at the guidance. And if it's applicable to their 15 plant design, they should use it.
16 And our intention with the Revision 5 was 17 not to -- was not to determine which plants it is or 18 is not applicable to. We didn't want to -- we wanted 19 to allow, you know, the staff doing the review and the 20 licensees or the applicants who are designing the 21 plants to determine whether the guidance is applicable 22 to them or not and use it if it is -- you know, if it 23 would be applicable.
24 MR. SCHULTZ: Good. And then, just to 25 expand on that a little bit, in any case, what the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
75 1 guidance is saying is that any change or any 2 application that's associated with CAP credit needs to 3 be evaluated on a -- needs to be evaluated by the 4 staff on a plant-specific basis and an application-5 specific basis.
6 MR. SALLMAN: Yeah. That's correct. I'm 7 not sure what the new plants, which one required CAP 8 credit. I haven't seen any. But I am expecting that 9 if a new plant comes, I think I -- I have seen some --
10 some -- for the Korean plant, which was which one, 11 EPR? Yeah, EPR.
12 Yeah. That one -- that was a PWR, and 13 that was applying CAP credit up to the vapor pressure 14 of the sump pressure. And that's all they needed.
15 They did not go beyond that vapor pressure.
16 MR. SCHULTZ: That's how it was finally 17 resolved and addressed.
18 MR. SALLMAN: Yes. Yes, yes, yes. I 19 talked to some of the new reactor staff, and they --
20 they told me that this is how they use CAP.
21 CHAIR MARCH-LEUBA: Steve, any more 22 comments?
23 MR. SCHULTZ: No. That's fine. Thank 24 you.
25 CHAIR MARCH-LEUBA: Okay. Anybody else NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
76 1 have more discussion or questions for the staff?
2 Any member of the public has any comments 3 they want to place on the record? If so, please 4 unmute yourself and -- and say it now. I don't see 5 any phone numbers. So if you are on a phone number, 6 you can just star six.
7 I hear no members of the public wanting to 8 make a comment, so this will end the presentation.
9 We are now going to talk administrative a 10 little bit. We expect to have a full committee 11 meeting on November 1st, which is a couple weeks from 12 now, and write a letter. And any other members wants 13 to oppose the idea of having a full committee meeting?
14 Because I assume we all say that we should write that 15 letter up. Yes?
16 I hear no opposition to writing a letter, 17 so we will write a letter on November 1st.
18 My proposal to the staff is that you 19 provide us a reduced presentation, at most half an 20 hour2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br />, during the full committee to give us plenty of 21 time to have discussions, and the committee on the 22 open session and prepare the letter.
23 So certainly summarize GSI-191 and FLEX, 24 but I am looking for one or two slides each and 25 concentrate on the CAP issues that we have been asking NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
77 1 you about.
2 And that's it. I am going to start 3 drafting a letter, which I have some basis for, but 4 this is going to be a difficult letter to write. To 5 the members, if anybody wants to provide me input on 6 which direction using the conclusions should go, or 7 provide me some write-up for the discussion, that 8 would be fine, too. Please do so soon, because we 9 need -- I mean, we have only really next week to work 10 on this.
11 I am going to propose to write the 12 conclusions maybe this week. Let me see. But I will 13 try to get the conclusions and socialize them with the 14 committee to see -- to get feedback. Then we'll get 15 the letter done and keep going from there.
16 Any more comments or questions? Because 17 we have plenty of time.
18 Okay. I hear nothing. Can somebody make 19 some noise and affirm that I am still connected?
20 MR. SCHULTZ: Yeah. We hear you.
21 CHAIR MARCH-LEUBA: Okay.
22 PARTICIPANT: We are still there, Jose.
23 CHAIR MARCH-LEUBA: All right.
24 MR. SCHULTZ: The Reg Guide has been 25 published.
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78 1 CHAIR MARCH-LEUBA: Yeah.
2 MR. SCHULTZ: We're not -- the committee 3 is not commenting on a draft guide that is going to be 4 modified. It would be commenting on proposed changes 5 in the future.
6 CHAIR MARCH-LEUBA: That is correct. So, 7 basically, we are commenting on Revision 6. If we 8 have a serious issue, we are commenting on Rev 6.
9 MR. SCHULTZ: Yes.
10 CHAIR MARCH-LEUBA: Now my -- my 11 inclination now -- we are still on the transcript. My 12 inclination now will be for reaffirming that we -- we 13 still support previous ACRS recommendations and 14 conclusions with the proviso that I believe the staff 15 has done a fantastic job recommending the methodology.
16 So at least if somebody uses CAP, we know 17 how to calculate it and what uncertainties are used.
18 But we still believe it's not -- it reduces the -- an 19 additional defense-in-depth layer, because the primary 20 basis for -- for the way we work with reactors is that 21 the layers, the protected boundaries are independent 22 from each other.
23 And now by allowing CAP, you are defending 24 the vessel with the containment. And they are not 25 independent anymore, but we will work on the language NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
79 1 and see if we can make it happen.
2 MR. SCHULTZ: Okay. Great idea, Jose.
3 CHAIR MARCH-LEUBA: Any comments?
4 MEMBER HALNON: Yeah. This is Greg. That 5 to me was the key issue coming out of this. It's not 6 so much that the physics don't -- don't allow for 7 pumps to survive as long as the pressure is there.
8 So, yeah, I need to think about that 9 portion a little bit more and understand how the 10 interplay between that and the other areas of defense-11 in-depth might be overlapping. Because you're 12 basically right, we're reducing the independence of 13 the barriers, which is a key portion of the defense-14 in-depth concept in my mind.
15 So, you know, I appreciate you voicing 16 that because that's what I was struggling with 17 throughout the presentation was the physics are fine 18 to me.
19 CHAIR MARCH-LEUBA: Yes. The calculations 20 are good.
21 MEMBER HALNON: Yeah. It's the concept 22 and the policy and then the overall effect on the 23 defense-in-depth barriers.
24 CHAIR MARCH-LEUBA: Yeah. And likely on 25 the letter we need to take a position about advanced NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
80 1 reactors. I like the position of the staff that says 2 that, well, if it applies to you, you use it. If 3 you're like NuScale and you don't have CCS pumps, 4 well, it doesn't apply to you.
5 And, Joy, you have some comments?
6 MEMBER REMPE: Well, it's just a thought 7 that was kind of in my mind, since we're -- we have 8 time to opine a bit.
9 The more -- the plants that are having 10 difficulty in dealing with GSI-191 often use a risk-11 based argument to get over that hump. And the request 12 that they evaluate this in a risk assessment is kind 13 of interesting. You know, what we had suggested that 14 was denied, and then yet that's what plants rely on 15 when they want to try and keep operating, is my 16 connection enough you can understand me?
17 CHAIR MARCH-LEUBA: Yeah. You sometimes 18 break up a little bit. But you're doing good now.
19 MEMBER REMPE: Oh, okay. Well, the --
20 anyway, just a thought that has been running through 21 the back of my mind that might be worth thinking about 22 for the letter, but it's up to you. I don't feel that 23 strongly about it, but it's just an interesting angle.
24 CHAIR MARCH-LEUBA: Yeah. God knows --
25 and you all know, too -- that I'm not a big proponent NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
81 1 of risk-informed anything. But for something like 2 this, I would like to be informed about the risk that 3 we are taking. I mean, it -- just saying no, we don't 4 want to do it because we're doing it 5 deterministically, it sounds hollow to me.
6 MEMBER PETTI: So I've been sitting 7 listening, and of course, you know, I wasn't involved 8 with any of the previous ACRS discussion. But it 9 seems like, if you just think about how different a 10 place we are in today than back when those letters 11 were written, in terms of risk-informed regulation 12 being more ingrained in the agency as part of its DNA, 13 the letter, you know, can serve a really good purpose 14 to reflect how different things are today than they 15 were back then, even the fact that there is different 16 Commissioners, right?
17 So some of that is important, and I -- I 18 do want to explore this defense-in-depth thing a 19 little bit more, because I -- what I really don't want 20 to see is a -- there's sort of a practicality to using 21 CAP. That's what the physics says, you know, would 22 actually happen.
23 And if you have to weaken defense-in-depth 24 a little in this small particular area, I just worry 25 about sort of rigid -- I call it safety theology if NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
82 1 you will in light of, you know, some tactical 2 considerations and how you balance that. To me, 3 that's important and something we can I think talk 4 about, you know, in full committee.
5 MEMBER BROWN: This is Charlie.
6 CHAIR MARCH-LEUBA: Yes. Yes.
7 MEMBER BROWN: I think I was here back 8 when we started all this stuff back in 2008, '09, and 9 all those -- the initial stuff. So was Dennis. And 10 we went -- all the math that we went through today, 11 the physics of the whole thing, was developed and 12 presented in spades. And my memory was that we were 13 very, very concerned as -- you know, I'm not much of 14 a risk-informed person either, so it's deterministic.
15 But our emphasis was really on what was 16 perceived as a -- in my mind, the gradual reduction in 17 defense-in-depth type -- the defense-in-depth type 18 concepts. And that's why the letter fundamentally --
19 that I think the last letter fundamentally said that.
20 It was a defense-in-depth type issue.
21 And we've -- I understand Dave's comment 22 relative to how things are more -- you know, the DNA 23 is changing in terms of the risk-informed mode. But 24 I think that needs to be tempered with the realistic 25 thought process of not degrading the committee's NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
83 1 emphasis on defense-in-depth either.
2 So I agree with Jose's fundamental thrust.
3 We may want to tailor it somehow, but that's -- Dennis 4 can chime -- he was there also, and I -- I'm not sure 5 -- Joy, I'm not sure when you -- you were there in 6 2011, weren't you?
7 MEMBER REMPE: Yeah. I started in 2010.
8 MEMBER BROWN: 2010. Okay. So you should 9 have been party to some of this discussion as well, if 10 I remember correctly.
11 MEMBER REMPE: You remember correctly.
12 MEMBER BROWN: Okay. So that's my memory.
13 You know, admittedly, I'm pretty old now, so -- but 14 the defense-in-depth issue weighed heavily on most of 15 the members' minds. I think it was a fairly unanimous 16 type approach. We did not -- it wasn't an eight to 17 seven vote in terms of the tone of the letter. So 18 that's also my memory.
19 But anyway, we didn't -- we don't have 20 transcription during that voting period, so I don't 21 know how we could recover that.
22 Dennis, do you have any other different 23 memories than I do?
24 MR. BLEY: No. That's pretty close. The 25 letter was -- letters were unanimous as far as I can NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
84 1 remember. I'm almost certain of that.
2 MEMBER BROWN: Yeah. That's my memory.
3 MR. BLEY: One of our members later became 4 a Commissioner and voted against this, and some have 5 held that against him ever since.
6 MEMBER BROWN: Was it George? You're 7 talking about George?
8 MR. BLEY: Yeah. You know, the risk here 9 is almost surely very low, but you ought to be more 10 sure than you can from that statement by me. That's 11 kind of it.
12 There had been a history of looking at CAP 13 as not much for a very short time, and very short 14 times had been just a few minutes, and then all of a 15 sudden we had an application that really went much 16 closer to losing that positive suction head.
17 And that time extended over a pretty long 18 period of time, at least by comparison to anything 19 they didn't look at before. And that was kind of a --
20 I think a shock for most people who first saw it.
21 But you had it right.
22 MEMBER BALLINGER: this is Ron. I mean, 23 is it time for us to say in this letter, or some other 24 place, that there is a -- in this case, there has been 25 a bit of a conflict between risk-informing and NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
85 1 deterministic and having a little bit of a gray area 2 there.
3 But that we ought to be sure that in the 4 future -- or we should say something that this is --
5 this issue -- not CAP, but this issue of risk-based or 6 risk-informed decision-making has the likelihood of 7 running up against defense-in-depth again. And we 8 ought to be sure that we say something like that, so 9 that we're on the record, because it might be 10 important in some future negotiation or discussion 11 that we should have said this.
12 MR. BLEY: I think one thing you -- you 13 folks who are still on the committee should consider 14 is we had a series of essentially debates with the 15 staff on this, and then we escalated it by sending a 16 letter to the Commission saying, you know, we can't 17 come to agreement with the staff.
18 And the Commission said, in terms of one 19 of the Commissioners at the time, reasonable assurance 20 is what we say it is, they said no, we're going with 21 the staff. So whatever you write ought to be -- keep 22 that in mind.
23 MEMBER BALLINGER: Yeah. I mean, we 24 should think about reminding people of this.
25 MR. SCHULTZ: This is Steve. The other NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
86 1 piece that -- when the staff -- the committee 2 presented its positions to the Commission, and the 3 staff did as well, in the staff's presentation to the 4 Commission -- and I think in the Commission's 5 deliberations -- I haven't read the statements by the 6 Commissioners.
7 But there were two things. One was the 8 staff promoting an approach -- the analytical 9 approach, which has been discussed today and now 10 documented in the Reg Guide.
11 The second piece of that was looking at 12 what the ACRS Committee was proposing, which was a 13 strongly-based probabilistic risk assessment, fully-14 based probabilistic risk assessment, including 15 external events, and so forth, that that was the 16 approach that was being proffered.
17 And the staff and the Commission both 18 evaluated what impact that would have on those 19 licensees that were -- would need to reevaluate their 20 use of containment accident pressure. And that was 21 part of their -- I mean, that was part of their 22 considerations. I don't know how much it affected 23 their determination, but it was -- it was fully 24 presented and evaluated by the staff in terms of what 25 it would take for the staff to put together such an NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
87 1 approach and what it would mean with regard to 2 licensees' not only reaction to it but the imposition 3 that that could impose on the licensees and whether 4 that was something that the Commission could do or 5 would do.
6 So it's worthwhile -- it's worthwhile 7 going back and reading -- reading the Commission's 8 statements and the staff's presentation to the 9 Commission at that time.
10 MR. BLEY: Yeah. I'd back Steve up on 11 that. But read the Commissioners' vote sheets.
12 They're still interesting, and kind of see where they 13 stand.
14 Probably the strongest feeling on the 15 committee at the time was unless there is some really 16 outrageously expensive reason not to do it, you ought 17 to fix this instead of coming in on -- relying on 18 analysis.
19 MEMBER BROWN: Amen. I remember that we 20 made those comments. It had to be really a very 21 expensive approach to making a fix, and so it should 22 be only under extenuating circumstances.
23 MR. BLEY: And I think the staff is -- I 24 have to go back and read their words, but from their 25 presentation it sounds like that's where they -- where NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
88 1 they stand. The first choice is to not have it as an 2 issue.
3 MR. SCHULTZ: I saw that in the -- in the 4 discussions, and it's reaffirmed in the guide.
5 CHAIR MARCH-LEUBA: Yeah. The guide says 6 if -- if it's practicable to fix it, fix it. And 7 then, if not, then start calculating.
8 Going back to what Steve said, I mean, 9 because on -- from the logical point of view, having 10 a Level 3 full-blown PRA, with all external events and 11 everything, it's very expensive. And we keep getting 12 comments back from industry, even on Part 53, saying 13 gee, I have a little two-megawatt reactor that doesn't 14 need it. Why do you want me to spend this many 15 million dollars on a PRA that doesn't do anything?
16 So we need to be conscious that even 17 though logically you should know the risk to the full 18 extent of the calculation of ability, sometimes it's 19 not worth the money.
20 MEMBER PETTI: Except that 52 requires it, 21 and 50 will -- if the rule passes, would also require 22 it for new plants. So --
23 CHAIR MARCH-LEUBA: Yeah.
24 MEMBER PETTI: -- there's an inconsistency 25 here. So --
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89 1 MR. BLEY: Well, you can found this stuff.
2 You know, if you're simple, you just assume the worst 3 case happens and see what -- what it looks like.
4 You know, the staff's position that the 5 most likely way you lose pressure is to -- to have 6 lost it initially by a bad valve lineup or something, 7 so there's a leak. That's true.
8 But the idea of a really strong seismic 9 event that could fail the containment and fail -- lead 10 to a LOCA somehow is -- while it's pretty unlikely, 11 but the combination is -- those kind of combinations 12 come up in external events, fires, or seismic events 13 -- in some old plants, wind events -- as the most 14 likely way you get those combinations of things 15 happening. So that's kind of where folks were coming 16 from back then.
17 MR. SCHULTZ: Yes, Dennis. That's what --
18 what's why -- that's what I read into the letter that 19 was prepared for the USPWR, APWR.
20 CHAIR MARCH-LEUBA: Yeah. And Steve sent 21 me a reference to the APWR letters, and I would 22 include them -- we'll include them back into the 23 SharePoint and we'll send you a link, so you can read 24 them. I haven't had time to read it myself. I just 25 saw it was APWR.
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90 1 Going back to a comment that Ron made half 2 an hour ago, the way I put it is we, in ACRS, have a 3 concern with this topic. We raised it, and we raised 4 it, and we elevated it all the way to the 5 Commissioners.
6 The Commissioners read it, understood it, 7 and voted, and they were against us. So, in a sense, 8 the issue has been resolved. I mean, we can continue 9 to complain, but the issue has been resolved.
10 MEMBER BALLINGER: It's not a complaint.
11 It's a reminder.
12 CHAIR MARCH-LEUBA: Yeah, yeah. It would 13 be nice if we can gain some broader perspective that 14 the problem applies -- the problem of not using risk 15 information applies not only to RG 182 but new 16 reactors, GSI-191, other things.
17 If we could frame it in -- in a lesson 18 learned for other topics, it would sound more 19 valuable, in my opinion.
20 MEMBER BALLINGER: Yeah. That's -- that 21 I think was what -- the point I was trying to make.
22 CHAIR MARCH-LEUBA: Yes.
23 MEMBER REMPE: So that's --
24 MEMBER BALLINGER: I mean, P&P is kind of 25 an academic exercise in some respects. But there may NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
91 1 be cases later on which aren't.
2 CHAIR MARCH-LEUBA: Joy?
3 MEMBER REMPE: Well, that's the reason I'm 4 thinking this angle about what's going on, like with 5 the Vogtle 1 and 2 request for GSI-191. They relied 6 on risk assessment. South Texas Project did this, 7 too, to get rid of GSI -- or get around GSI-191.
8 It's so related to this topic. I think 9 it's a way to broaden it and point out that the more 10 difficult ones have had to rely on risk assessment.
11 CHAIR MARCH-LEUBA: Yeah. I mean, it's 12 not fair that the applicants get to rely on risk 13 assessment only when they want to, only when it's good 14 for them.
15 MEMBER REMPE: Yes. That's where I'm kind 16 of thinking of going, but anyway, it's just an idea.
17 CHAIR MARCH-LEUBA: This letter is going 18 to be very difficult, speaking of which, Joy, we have 19 scheduled it for November. But the guide has been 20 issued. If we are extremely busy and we cannot finish 21 it in November, we can do it in December, we can do it 22 in February.
23 MEMBER REMPE: This is all fine. Right 24 now, we have three letters for November, and I've 25 actually seen one draft and I think it's in really NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
92 1 good shape. But I think Dave's letter will be more 2 difficult on Part 53, and this one may be.
3 But, you know, let's just see what we can 4 get done. We have an extra half day in December.
5 CHAIR MARCH-LEUBA: I was just offering 6 the fact that the guide was issued in August, and 7 there is no hurry for our letter.
8 MEMBER REMPE: Sure. I meant to say, by 9 the way, an extra half day in November. So, and we 10 have time in November -- or December also, so let's 11 see what we can do.
12 MEMBER HALNON: Jose, you stated that 13 licensees shouldn't be able to just use risk 14 information anytime they want to. That doesn't apply 15 in this case. These plants that couldn't solve 16 GSI-191 deterministically had to turn to the risk 17 because of the -- it's not just because they wanted 18 to. It's because it -- that was the best course of 19 action.
20 I think that licensees should be able to 21 use risk information if the deterministic and 22 mechanistic areas of -- you know, just putting in 23 bigger strainers is not possible. So I don't know.
24 I just -- I'm not sure that's what you meant, but it 25 sounded to me like you meant --
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93 1 CHAIR MARCH-LEUBA: That's not what I 2 meant. What I meant is I -- I don't know what the 3 risk is when you allow CAP use. We suspect it's very 4 small, but I don't know.
5 MEMBER HALNON: Okay. I got it. I 6 thought you were making a broader statement, so I 7 apologize.
8 CHAIR MARCH-LEUBA: Okay. I wanted to 9 make another broad statement, Joy, and this is for 10 your ears. This was -- half an hour was fantastic.
11 We should have these discussions of the two committees 12 more often, because more often than not, the committee 13 chairman --
14 (Simultaneous speaking.)
15 CHAIR MARCH-LEUBA: -- then we complain 16 about the commas and whiches (phonetic). We should do 17 this more often. Just offering that for thought.
18 MEMBER REMPE: I agree. It's nice to have 19 that flexibility.
20 MEMBER BALLINGER: But, you know, it 21 really depends on the subject I think.
22 CHAIR MARCH-LEUBA: Yeah.
23 MR. BLEY: Well, it does, you know, but 24 the committee is offering in a hurry to wrap up these 25 --
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94 1 MEMBER PETTI: I'm on a call that's going 2 to end soon, yeah.
3 MEMBER REMPE: Dave, did you know you're 4 -- you need to mute.
5 MEMBER PETTI: So should we just set a 6 time for you to --
7 MEMBER REMPE: David, I'm going to mute 8 you. Okay.
9 CHAIR MARCH-LEUBA: Okay. I'm going to 10 mute everybody. Any more discussions?
11 MR. BLEY: Well, I was just going to make 12 a suggestion to the committee. In recent few years, 13 we've been really focused on not extending a meeting 14 beyond the expected closing time and hurrying to 15 close.
16 If you go back 20, 30 years, when I used 17 to come to the committee, if there was an issue, 18 they'd keep going until, you know, 10:00 at night to 19 -- to make sure that they get everything worked out 20 that they wanted to work out. And I don't see a 21 problem with that, but that's up to you folks.
22 CHAIR MARCH-LEUBA: Yeah. I remember 23 being trained on using the side door on Saturdays. We 24 hadn't used it in the last four years.
25 Any more comments, guys?
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95 1 MEMBER REMPE: Well, I have a comment for 2 Ron that I'm hoping that November subcommittee SHINE 3 will have that day when we're going through the memos 4 and the letter and we'll have a similar type of 5 discussion for him.
6 MEMBER BALLINGER: I have absolutely no 7 doubt whatsoever.
8 (Laughter.)
9 MEMBER REMPE: Okay. Thank you, Ron. I 10 just thought I'd kind of point that out.
11 CHAIR MARCH-LEUBA: Okay. So, with that, 12 I'm going to let the Court Reporter go home. The 13 official part of this meeting is over. You can -- you 14 can stop it now.
15 (Whereupon, the proceedings in the above-16 entitled matter went off the record at 11:53 a.m.)
17 18 19 20 21 22 23 24 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1716 14th STREET, N.W., SUITE 200 (202) 234-4433 WASHINGTON, D.C. 20009-4309 www.nealrgross.com
Reg Guide 1.82, Revision 5 GSI-191 Issues ACRS T/H Subcommittee, October 20, 2022 Ahsan Salman Steve Smith 1
RG 1.82 Changes in Rev. 5
- GSI-191 (Main body of RG and Appendix A)
New information on the effects of debris on long-term core cooling Added specific information and references to evaluate debris in-vessel effects
- Use of CAP (Appendix B)
Added new Appendix B - guidance on the use of CAP in determination of NPSH margins Applies to existing and new BWRs and PWRs licensed under 10 CFR Parts 50 and 52 Some plants are licensed to use CAP for determining available NPSH for ECCS and CHR pumps RG 1.1 states only containment pressure prior to LOCA should be used in NPSH calcs RG 1.1 withdrawn (4/2015); new CAP guidance to be included in RG 1.82, Rev 5.
2
Background
- GSI-191 Summary
- Regulatory Guide (RG) 1.82 Revisions Related to GSI-191
- In-Vessel Guidance Updates (2019)
- Penetration Testing Guidance
- Improved Clarity and Detail
- Updated Knowledge Base Report (2014)
- BWR Evaluation of Lessons Learned (2018)
- Updated Jet Testing (2012)
- Test Debris Preparation Guidance (2012) 3
GSI-191 Summary
- Closed in 1985
- Several generic communications after 1985 regarding debris and adequate NPSH margins
- Some were BWR specific
- Through 1990s many cases of debris problems
- Affecting pump operation
- In containment and pumps (and suction lines)
- Several cases of damaged strainers
- Debris could go downstream
- BWRs evaluated and closed issue in 2000 4
GSI-191 Summary
- Opened GSI-191 in 1996 for PWRs
- NRC completed review in 2002 finding sump clogging to be a credible concern
- Issued BL 03-01 and GL 04-02 requesting
- Licensees to take mitigative actions
- Provide assurance that long-term core cooling (LTCC) would be successful considering the effects of debris
- GSI remained open because some technical issues were not fully understood 5
GSI-191 Summary
- Licensees evaluated debris effects and replaced strainers with models with much greater area and better filtering designs
- Chemical and In-vessel effects were not well understood
- Methodology for chemical effects accepted in 2007
- Final methodology for in-vessel effects developed in 2019
- Upon establishing accepted method for in-vessel effects, GSI-191 was closed in 2019 (ML19203A303)
- Licensees must still respond to GL 04-02 6
GSI-191 Summary
- GL 04-02 Plant Status
- 9 low fiber plants closed using original in-vessel guidance
- 10 plants closed out deterministically after 2019 in-vessel guidance issued
- 7 plants have deterministic submittals under review
- 2 plants - NRC awaiting final deterministic submittals
- Risk-informed resolution
- 2 plants closed
- 2 plants under review (1 of these in concurrence)
- NRC Awaiting LARs from 2 plants 7
Reg Guide 1.82 Changes for GSI-191
- Reference to Draft RG 1.229 for RI evaluation of debris effects (ML15335A179)
- BWROG stating issues reviewed, no further concerns - ML17326A393
- NRC Staff Technical Evaluation - ML18058A602
- NRC letter accepting BWROG position - ML18078A061 8
Reg Guide 1.82 Changes for GSI-191
- NRC In-vessel Downstream Effect (IVDE) Safety Significance TER -
- Evaluates risk of physical aspects of in-vessel debris effects on long-term cooling
- Discussed with ACRS TH Subcommittee in April and September 2019
- NRC Staff Review Guidance for IVDEs - ML19228A011
- Provides guidance commensurate with plant conditions and reactor/fuel design ability to accommodate debris in the vessel
- Relies on findings from WCAP-17788-P and TER (above)
- Discussed with ACRS TH Subcommittee in May 2021 (Vogtle LAR) 9
Reg Guide 1.82 Changes for GSI-191
- WCAP-17788-P, Revision 1 - Package - ML20010F181, Volume 1 - ML20010C854
- Significant headloss testing, chemical testing, and TH analysis
- No SE written by NRC, but found to provide significant increase in knowledge of behavior of the system with debris effects
- NRC validated TH work using TRACE
- Added a few other references noted on slide 3 10
RG 1.82 Status With Respect to GSI-191
- Revision 5 to RG 1.82 was performed after the closure of GSI-191
- RG 1.82, Rev 5 is a complete guidance document for the effects of debris on long-term core cooling
- Additional guidance may be issued as the result of the 10CFR50.46c rulemaking currently with the Commission
- RG 1.229 on risk-informed evaluation of debris on LTCC
- Unlikely for the RG to be used after the rule is finalized
- RG contingent upon the rulemaking and may be left as-is, deleted or revised 11
Reg Guide 1.82, Rev. 5 Public Comments
- NRC received 4 sets of public comments from 3 entities
- Comments received in areas of:
- Applicability and Scope - relevance to alternate designs
- NRC position is that RG is guidance, only applied where appropriate
- Rev. 5 not intended to cover new reactors except when guidance is applicable
- Definitions, Clarifications, and References
- NRC made changes where appropriate
- Add Risk-Informed Guidance
- No changes made, awaiting 50.46c rulemaking 12
Reg Guide 1.82, Rev. 5 Public Comments
- Comments in the area of:
- Specificity of Methodology and Failure Criteria
- NRC concluded methodology is described as desired
- Requested additions assumed that information included as an example in a SECY paper referenced in the RG was intended to have global applicability to all plants
- Made reference in the SECY public in ADAMS
- Comments suggested including methods for evaluations outside the scope of the RG
- No changes made
- Editorial comments in Appendix B
- Incorporated 13
FLEX Equipment - Defense-in-Depth
- FLEX strategies are designed for beyond-design-basis external events initiated by natural phenomena
- Not intended or reviewed for response to postulated accidents
- However, some equipment may be available for accident response DID
- There is adequate FLEX electrical power (or diesel) for all equipment
- BWR FLEX includes equipment for direct connection to the RCS and the ability to vent containment if needed
- BWR strategy is typically to vent containment for pressure reduction, if needed
- PWR FLEX RCS injection only has low volume pumps with connections to the RCS
- For Shutdown or low leakage only, includes borated water supply
- Decay heat is removed via the steam generators with higher volume pumps
- Connecting steam generator FLEX pumps to the RCS may be possible for some plants but has not been pre-planned or verified to be feasible in general
- No pre-determined strategy for containment pressure reduction 14
FLEX Equipment - Defense-in-Depth
- Strainer blockage
- For most strainer blockage events RCS pressure would be low
- BWRs have deployable FLEX capability to supply the RCS
- Unclear if PWRs would be able to reconfigure the SG FLEX pumps and provide piping connections to inject large volumes of water within required timeframe
- PWRs have low volume injection (typically 10s of gpm) for shutdown conditions or for pump seal leakage that are pre-configured for connection
- May need to consider containment venting and water level control strategies, etc.
- Effectiveness depends on plant-specific equipment capacities, layouts, connections, etc.
- No boration available at higher flow rates
- Lower flows could be adequate if it takes a long time for strainer blockage to occur
- Depends on plant-specific pump capacity 15
FLEX Equipment - Defense-in-Depth
- This scenario is likely very similar to the strainer blockage case
- Small energy release to containment from RCP seals
- Similar constraints to those for the strainer blockage case
- PWRs would have challenges like those for a blocked strainer 16
RG 1.82, REVISION 5, APPENDIX B GUIDANCE FOR THE USE OF CONTAINMENT ACCIDENT PRESSURE IN DETERMINING THE NET POSITIVE SUCTION HEAD MARGIN FOR EMERGENCY CORE COOLING SYSTEM PUMPS AND CONTAINMENT HEAT REMOVAL PUMPS IN BOILING WATER REACTORS AND PRESSURIZED WATER REACTORS
CONTENTS
- 1. Background
- 2. Key Terms
- 3. Role of ECCS and CHR Pumps
- 4. Regulatory Requirements and Guidance
- 6. Cavitation Erosion
- 7. Effect of Non-Condensable Gas on Pump Mechanical Performance
- 8. Loss of Containment Isolation and Containment Leakage
- 9. Containment Cooling if CAP Is Used
- 10. Illustration of hatm and CAP Available
- 11. Quantifying NPSH Margin
- 12. Guidance Summary
- 13. EPU LARs Approved (Using CAP Guidance in SECY-11-0014)
- 14. Acronyms and Symbols 2
- 1. Background
- CAP Issue Use of CAP in determining NPSHa for ECCS and CHR pumps critiqued by the ACRS Published regulatory guidance was not clear and consistent
- EPU LAR reviews discontinued because of CAP issue Browns Ferry Units 2 & 3 EPU (15%), June 2004, 5% was previously approved Browns Ferry Unit 1 EPU (20%); only 5% was approved, June 2004, Monticello EPU, October 2009
- BWROG submitted topical report NEDC-33347P / NEDO-33347 (2/2008) providing a standard approach for requesting CAP in NPSH analysis.
- are included in guidance)
CAP credit should be limited in amount and duration
- Revise RG 1.82 to incorporate guidance.
- Operator actions to control CAP should be reliable, risk should be acceptably small.
3
Background (Continued)
SRP 6.2.2 should be revised to state if CAP is granted based on risk info.
- Before CAP credit, licensees to justify impractical to modify plant For licensing, CAP deterministic calc should be complemented by PRA
- Support staff reassessment of problems with NPSHa NPSHr
- Margin (NPSHa - NPSHr) to consider uncertainty in NPSHr
- Hardware modification or risk studies not needed for small CAP credit (in deterministic analysis)
If no CAP credit is needed for special events 95/95 lower tolerance bound for LOCA using acceptable method shows no CAP credit is needed.
Staff PRA studies presented are helpful, to assess risk need plant-specific studies.
Staff is reviewing ACRS recommendations Submittal of BWROG report a significant milestone Address policy issues before including risk in non-risk informed LARs.
4
Background (Continued)
- ACRS Letter to Commission Chairman (2/17/2011)
Disagreement between ACRS and staff ACRS Position - CAP credit is a serious compromise of independence of prevention and mitigation which is a basic element of defense-in-depth philosophy; CAP is granted only if design cannot be practicably altered.
Staff Position - Analysis showing CAP provides adequate NPSH is as acceptable as design change that eliminates the need for CAP credit. No regulatory basis to request licensees to provide plant-specific risk information to assess the challenge to defense-in-depth.
- Pump Consultant - Allan R. Budris Reports (October & November 2009)
Task # 1- Review Sulzer Browns Ferry RHR and LPCS pump report (ML062920156), and evaluate overall methods for NPSHr Task # 2 - Determine accuracy and uncertainty in NPSHr3%
Task # 3 - Evaluate technical justification for allowing pump operation in cavitation Task # 4 - Evaluate NRC criteria of basing CAP at zero NPSH margin (Nov 2009) 5
Background (Continued)
- SRM (6/25/2010) & SECY-11-0014 Staff paper to discuss where staff aligns and where it disagrees with ACRS including risk, defense-in-depth and hardware changes to eliminate CAP.
Staff responds to SRM (1/31/2011); SECY-11-0014; options for Commission vote:
Option 1, Staff approach, deterministic, uncertainty and margins Option 2, ACRS approach includes staff approach + plant specific PRA Commission votes (3/2011), Option 1 - four votes; Option 2- one vote Commission approved (3/15/2011) SECY-11-0014 with Option 1
- Commission directed staff to credit CAP using guidance in SECY-11-0014, Enclosure 1.
- Draft guidance based on SECY-11-0014 sent to PWROG and BWROG (2/25/2011)
- RG 1.82, Revision 5, Appendix B is based on SECY-11-0014, Enclosure 1.
6
- 2. Key Terms (RG Sections B-1 and B-6)
NPSH Available (NPSHa) (RG Figure B-6)
BWR Suppression Chamber or PWR Sump
- NPSHa = hatm + hstatic hloss hvp
- hvp = vapor presure at suppression pool or sump water temperature
- CAP = pressure greater than containment pressure prior to accident or an event.
7
Key Terms (Continued)
NPSH Required (NPSHr)
- NPSHr3% according to ANSI/HI 14.6-2016 is the NPSH that results in cavitation sufficient to reduce the pump total dynamic head (TDH) by 3%.
- NPSHr3% (from factory test) depends on pump design, flow and water temperature.
- In-plant installed pump NPSHr may differ from NPSHr3% due to difference in test conditions and plant conditions.
- NPSH Margin = (NPSHa - NPSHr) 8
Key Terms (Continued)
- NPSH Margin Ratio = (NPSHa / NPSHr)
- Cavitation Occurrence of vapor-filled cavities in a liquid (Grist, Cavitation and the Centrifugal Pump: A Guide for Pump Users (RG Ref. B-1)).
In a pumped liquid, cavitation is the formation of vapor-filled cavities in the liquid flow due to a decrease in the local static pressure below its vapor pressure.
9
Cooling of RCS during shutdown (RHR)
Suppression pool cooling normal operation when heat is added (RHR)
LPCI and core spray in reactor following LOCA (RHR and LPCS)
Suppression pool cooling during LOCA or special events (RHR)
Containment spray for containment cooling and fission product removal (RHR)
Safety injection following LOCA during sump recirculation phase (RHR)
Containment spray following LOCA to cool containment & remove fission products (CS)
RCS cooling during shutdown (RHR) 10
- 4. Regulatory Requirements and Guidance (RG Section B-3)
- 10 CFR Part 50. Appendix A GDC 35, Emergency core cooling, GDC 38, Containment heat removal,
- Guidance in this RG Section C.1.3.1 includes:
RG 1.1 position Conservative calculation of transient NPSHa and available CAP.
Prototypical test for crediting pump operation in cavitation Calculation of pumped water temperature Head loss in the suction strainer and piping
- Uncertainty Analysis & NPSH Margin For NPSH margin, current approach assigns bounding inputs for LOCA containment temperature, NPSH analysis For DBA, in BWROG topical report NEDC-33347P-A/NEDO-33347-A, CAP is determined by Monte Carlo calculation.
For special events, realistic inputs may be used, and licensee to quantify uncertainty.
11
- NPSHr should correspond to acceptable level of cavitation that allows the pump to perform its safety function for accident duration and recovery time.
- NPSHr3% is typically obtained by factory testing of the actual pump or a similar one in accordance with ANSI/HI 14.6-2016.
- NPSH margin = (NPSHa - NPSHreff), where NPSHreff = NPSHr3% + uncertainties
- NPSH margin should be greater than or equal to zero.
- Difference in the factory test NPSHr3% and field NPSHreff is due to the following:
Pump speed (because of motor slip)
NPSHr varies as square of the pump speed, which changes with motor slip.
Pump may operate at slightly higher speeds in field compared to a factory test speed Water temperature The NPSHr decreases as water temperature increases.
Factory tests mostly at lower temps than field resulting in increased NPSH margin.
Effect of water temperature should not be considered in the field NPSHr 12
Use of CAP in Determining NPSH Margin (Continued)
Suction piping configuration For acceptable pump operation, uniform inlet flow, free of swirl, and vortices.
Short and straight suction piping for better performance, may not be possible in field Pressure loss in suction piping should be minimized to obtain the maximum NPSHa.
Air content of water (may be lower in the vendors test than in the field)
Dampens the effect of cavitation It increases the NPSHr, Release of the noncondensable gases affects the NPSH margin May interfere with the water cooling of pump seals.
- Licensee to determine and propose uncertainty in NPSHr3%
- For BWRs SBO, ATWS, and Appendix R fire events NPSHr3% may be used for NPSH margin, and realistic assumptions may be used for NPSHa analysis
Use of CAP in Determining NPSH Margin (Continued)
- Negative NPSH margin is acceptable if tests done to demonstrate that the pump will perform its safety function(s), and following should apply:
- Operation for a limited duration (less than 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />)
- Actual pump or similar (model, size, materials, and seal/flush system) is tested.
- Tested at same speed as at the plant site.
- Tested at the actual predicted NPSHa,
- Test duration is for the time during which NPSH margin is negative
- Flow and discharge head should be greater than required for safety analysis.
14
- 6. Cavitation Erosion (RG Section B-5 and Figure B-4)
- Insufficient NPSH margin results in pitting of impeller blade and other pump parts due to condensation caused by vapor bubble implosion near a solid surface.
- Visual studies, acoustical measurement, field experience shows maximum erosion rate occurs at NPSHa value between NPSHr3% and cavitation inception (margin ratio 4)
- Pump tests indicate that the zone of maximum erosion rate lies between NPSH margin ratios of 1.2 and 1.6 for pumps operating outside of the zone of suction recirculation 15
- 7. Effect of Non-Condensable Gas on Pump Mechanical Performance (RG Section B-7)
- Large quantity of entrained air from suction source, vortices, or released from solution can affect pump mechanical performance.
- Configuration of the PWR sump or BWR suppression pool should consider eliminating entrainment of air (by sprays) and vortices.
- NUREG-0897 - vortices decay to negligible levels within 14 pipe diameters.
- For NPSHa close to NPSHr3%, vapor or entrained air could damage the shaft seal faces, therefore dual seal with external cold water flush system should be provided.
- If CAP used is determined assuming NPSHa = NPSHreff, then safety analysis flow should be equal to or less then flow resulting from a 3-percent decrease in TDH.
- Time of operation in the region of maximum erosion should be limited.
16
- 8. Loss of Containment Isolation and Containment Leakage (RG Section B-7)
If CAP is used, the licensees should-
- Demonstrate loss of containment integrity and loss of containment isolation cannot occur.
- Reduce the likelihood of a preexisting leak by determining minimum leakage rate sufficient to lose the needed CAP.
- Propose a method to determine whether the actual leakage rate exceeds the calculated.
- Propose a time limit plant can operate without losing the needed CAP.
- Licensees should demonstrate sprays and coolers will not reduce needed CAP.
- Operator action to control the CAP by sprays or coolers is acceptable if justified.
- Adequate guidance should be included in the operating procedures.
17
Tsat (atmospheric pressure)
Perform conservative containment analysis to determine Tpmax and transient ht, Tp and hvp - [A]
- If Tpmax > Tsat and needed CAP (hvp - hmin)
Determine the needed CAP for NPSHa = NPSHreff Perform NPSH analysis - [B]
[A] and [B] is the design basis
Determine the needed CAP for NPSHa = NPSHreff Perform statistical (Monte Carlo 95/95) containment and NPSH analysis to determine margin Perform NPSH analysis - [C]
[A] and [C] is the design basis 18
Perform realistic analysis to determine margin NRC calculation showed conservative NPSH values are close to 95/95 lower tolerance limit of Monte Carlo calculation of same problem.
Monte Carlo lower tolerance limit of NPSHa is acceptable for conservative case NPSHr should include its uncertainty
- BWR special events Realistic NPSH analysis is acceptable, i.e., nominal inputs based instead of TS LCOs or bounding inputs Use conservative inputs if realistic values are not available NPSHr may be used without uncertainty
- 12. Guidance Summary (RG Section B-9)
- For BWR special events, NPSHr3% may be used to calculate margin
- Maximum flow rate for NPSHa analysis flow rate used in safety analysis
- Loss of containment integrity (venting) should not occur during CAP use.
- NRC-approved operator action to control CAP is acceptable.
- Negative NPSH margin is acceptable if tests done to demonstrate that the pump will perform its safety function(s) with certain conditions.
- To reduce the likelihood of a preexisting containment leak, following should apply:
Determine the minimum leakage rate to lose CAP needed for +ve NPSH margin.
Propose a method to determine leakage rate.
Propose a time limit for operation while the actual leakage exceeds rate determined
- Zone of maximum erosion rate should be between NPSH margin ratios of 1.2 and 1.6.
- PWRs, CAP options are: use the vapor pressure corresponding to the sump water temperature or use a procedure similar to the BWROG Monte Carlo method.
- Mission time for pump using CAP to include recovery time from the accident.
20
- 13. EPU LARs Approved (Using CAP Guidance in SECY-11-0014)
- Monticello LAR review reactivated
- Browns Ferry Units 1, 2, & 3 LAR resubmitted
- Other LARs following CAP Guidance in SECY-11-0014 include Peach Bottom 2 & 3 (modified hardware)
Grand Gulf Turkey Point 3 & 4 St Lucie 1 & 2 Point Beach Units 1 & 2 21
- 14. Acronyms and Symbols Acronym Description Symbol Description ATWS Anticipated Transient Without Scram hatm Containment pressure head BWR Boiling Water Reactor hmin Minimum pressure head at normal plant operation BWROG BWR Owners Group ht CAP head CAP Containment Accident Pressure hvp Transient vapor pressure at supp pool (BWRs) or CS Containment Spray sump water (PWRs) temperature during an accident DBA Design Basis Accident hloss Strainer and pump inlet piping head loss CHR Containment Heat Removal hstatic Static head at pump inlet ECCS Emergency Core Cooling System Tpmax Maximum suppression pool or sump water temperature EPU Extended Power Uprate Tsat Saturation temperature at hmin LAR License Amendment Request LOCA Loss-of-Coolant Accident LPCI Low Pressure Coolant Injection LPCS Low Pressure Core Spray NPSH Net Positive Suction Head NPSHa NPSH Available NPSHr NPSH Required NPSHr3% NPSHr corresponding to 3% pump TDH drop at a given flow NPSHreff NPSHr Effective OG Owners Group PWR Pressurized Water Reactor RCS Reactor Coolant System RG Regulatory Guide RHR Residual Heat Removal SBO Station Black Out TDH Total Dynamic Head 22